diff --git a/.changeset/html-block-editor.md b/.changeset/html-block-editor.md
new file mode 100644
index 000000000..3aa0fc206
--- /dev/null
+++ b/.changeset/html-block-editor.md
@@ -0,0 +1,6 @@
+---
+"emdash": minor
+"@emdash-cms/admin": minor
+---
+
+First-class HTML block in the admin editor. The existing `htmlBlock` Portable Text type (produced by the WordPress and Contentful importers) is now a fully editable block in the rich-text editor. Authors can insert an HTML block via the `/html` slash command, edit raw HTML in a textarea, and toggle a sanitized preview. Imported `htmlBlock` content that previously fell through to an opaque `pluginBlock` placeholder is now rendered in the same editable UI. The inline (visual-editing) editor preserves HTML blocks as read-only placeholders to prevent data loss.
diff --git a/docs/src/content/docs/guides/working-with-content.mdx b/docs/src/content/docs/guides/working-with-content.mdx
index 3afe5b3be..f5719c5e0 100644
--- a/docs/src/content/docs/guides/working-with-content.mdx
+++ b/docs/src/content/docs/guides/working-with-content.mdx
@@ -63,6 +63,7 @@ EmDash's editor supports:
 - **Links** - Internal and external
 - **Images** - Insert from media library
 - **Code blocks** - With syntax highlighting
+- **HTML blocks** - Raw HTML for custom embeds and widgets
 - **Embeds** - YouTube, Vimeo, Twitter
 - **Sections** - Reusable content blocks via `/section` command
 
@@ -75,6 +76,7 @@ Type `/` to access quick insert commands:
 | `/section`                   | Insert a reusable section           |
 | `/image`                     | Insert an image from media library  |
 | `/code`                      | Insert a code block                 |
+| `/html`                      | Insert a raw HTML block             |
 
 ### Keyboard Shortcuts
 
@@ -99,6 +101,61 @@ Type `/` to access quick insert commands:
 
 5. Click **Insert**
 
+### HTML Blocks
+
+Use `/html` to insert a raw HTML block. This is useful for embedding third-party widgets, custom markup, or content that doesn't fit the standard block types. HTML blocks are also created automatically when importing content from WordPress or Contentful that contains markup EmDash can't convert to native Portable Text blocks.
+
+<Aside type="caution">
+	HTML blocks are sanitized before rendering on the frontend to prevent XSS attacks. By default, iframes are only allowed from `www.youtube.com` and `player.vimeo.com`. Iframes from other providers (Cloudflare Stream, Loom, Wistia, Google Maps, etc.) will be stripped during sanitization.
+</Aside>
+
+To allow iframes from additional providers, override the `htmlBlock` component in your Portable Text rendering:
+
+```astro
+---
+// src/components/MyHtmlBlock.astro
+import sanitizeHtml from "sanitize-html";
+
+const { node } = Astro.props;
+
+if (!node?.html) {
+  return null;
+}
+
+const sanitized = sanitizeHtml(node.html, {
+  allowedTags: [...sanitizeHtml.defaults.allowedTags, "img", "span", "iframe"],
+  allowedAttributes: {
+    ...sanitizeHtml.defaults.allowedAttributes,
+    "*": ["class", "id", "data-*", "style"],
+    iframe: ["src", "width", "height", "frameborder", "allow", "allowfullscreen"],
+    img: ["src", "srcset", "alt", "title", "width", "height", "loading"],
+  },
+  allowedIframeHostnames: [
+    "www.youtube.com",
+    "player.vimeo.com",
+    "iframe.videodelivery.net", // Cloudflare Stream
+    // Add your providers here
+  ],
+});
+---
+
+<div class="html-block" set:html={sanitized} />
+```
+
+Then pass it to `<PortableText>`:
+
+```astro
+---
+import { PortableText } from "emdash/ui";
+import MyHtmlBlock from "../components/MyHtmlBlock.astro";
+---
+
+<PortableText
+  value={post.data.content}
+  components={{ type: { htmlBlock: MyHtmlBlock } }}
+/>
+```
+
 ## Editing Content
 
 1. Navigate to the collection containing the content
diff --git a/packages/admin/src/components/PortableTextEditor.tsx b/packages/admin/src/components/PortableTextEditor.tsx
index b7b3a0ddb..8e54a8874 100644
--- a/packages/admin/src/components/PortableTextEditor.tsx
+++ b/packages/admin/src/components/PortableTextEditor.tsx
@@ -56,6 +56,7 @@ import {
 	Minus,
 	LinkBreak,
 	ArrowSquareOut,
+	BracketsAngle,
 	CodeBlock,
 	Stack,
 	Eye,
@@ -93,6 +94,7 @@ import { CaretNext } from "./ArrowIcons.js";
 import { BlockKitMediaPickerField } from "./BlockKitMediaPickerField";
 import { CodeBlockExtension } from "./editor/CodeBlockNode";
 import { DragHandleWrapper } from "./editor/DragHandleWrapper";
+import { HtmlBlockExtension } from "./editor/HtmlBlockNode";
 import { ImageExtension } from "./editor/ImageNode";
 import { MarkdownLinkExtension } from "./editor/MarkdownLinkExtension";
 import {
@@ -277,6 +279,15 @@ function convertPMNode(node: {
 			};
 		}
 
+		case "htmlBlock": {
+			const rawHtml = node.attrs?.html;
+			return {
+				_type: "htmlBlock",
+				_key: generateKey(),
+				html: typeof rawHtml === "string" ? rawHtml : "",
+			};
+		}
+
 		case "image": {
 			const attrs = node.attrs ?? {};
 			const provider = attrStr(attrs.provider);
@@ -640,6 +651,14 @@ function convertPTBlock(block: PortableTextBlock): unknown {
 		case "break":
 			return { type: "horizontalRule" };
 
+		case "htmlBlock": {
+			const htmlBlock = block as { _type: "htmlBlock"; _key: string; html?: string };
+			return {
+				type: "htmlBlock",
+				attrs: { html: htmlBlock.html || "" },
+			};
+		}
+
 		case "table": {
 			const tableBlock = block as {
 				_type: "table";
@@ -922,6 +941,21 @@ const defaultSlashCommands: SlashCommandItem[] = [
 			editor.chain().focus().deleteRange(range).toggleCodeBlock().run();
 		},
 	},
+	{
+		id: "htmlBlock",
+		title: msg`HTML`,
+		description: msg`Insert raw HTML`,
+		icon: BracketsAngle,
+		aliases: ["html", "raw", "markup"],
+		command: ({ editor, range }) => {
+			editor
+				.chain()
+				.focus()
+				.deleteRange(range)
+				.insertContent({ type: "htmlBlock", attrs: { html: "" } })
+				.run();
+		},
+	},
 	{
 		id: "divider",
 		title: msg`Divider`,
@@ -2088,6 +2122,7 @@ export function PortableTextEditor({
 				underline: {},
 			}),
 			CodeBlockExtension,
+			HtmlBlockExtension,
 			ImageExtension,
 			MarkdownLinkExtension,
 			PluginBlockExtension,
diff --git a/packages/admin/src/components/editor/HtmlBlockNode.tsx b/packages/admin/src/components/editor/HtmlBlockNode.tsx
new file mode 100644
index 000000000..18cd06190
--- /dev/null
+++ b/packages/admin/src/components/editor/HtmlBlockNode.tsx
@@ -0,0 +1,202 @@
+/**
+ * HTML block node for the admin editor.
+ *
+ * Renders a first-class `htmlBlock` in the Portable Text editor with:
+ * - A textarea for editing raw HTML source
+ * - Selection ring, drag handle, and delete action
+ *
+ * Modeled on `PluginBlockNode.tsx` (atom node with React node view) and
+ * the existing `{ _type: "htmlBlock", _key, html }` Portable Text shape
+ * used by the WordPress and Contentful importers.
+ */
+
+import { Button } from "@cloudflare/kumo";
+import { useLingui } from "@lingui/react/macro";
+import { BracketsAngle, DotsSixVertical, Trash } from "@phosphor-icons/react";
+import { Node, mergeAttributes } from "@tiptap/core";
+import type { NodeViewProps } from "@tiptap/react";
+import { ReactNodeViewRenderer, NodeViewWrapper } from "@tiptap/react";
+import * as React from "react";
+
+import { cn } from "../../lib/utils";
+
+// ---------------------------------------------------------------------------
+// Node View
+// ---------------------------------------------------------------------------
+
+function HtmlBlockNodeView({ node, updateAttributes, selected, deleteNode }: NodeViewProps) {
+	const { t } = useLingui();
+	const html = typeof node.attrs.html === "string" ? node.attrs.html : "";
+	const [draft, setDraft] = React.useState(html);
+	const textareaRef = React.useRef<HTMLTextAreaElement>(null);
+
+	// Sync draft when the stored html changes from outside the node view.
+	React.useEffect(() => {
+		setDraft(html);
+	}, [html]);
+
+	// Auto-resize textarea to fit content.
+	React.useEffect(() => {
+		const el = textareaRef.current;
+		if (el) {
+			el.style.height = "auto";
+			el.style.height = `${el.scrollHeight}px`;
+		}
+	}, [draft]);
+
+	const commitHtml = React.useCallback(
+		(value: string) => {
+			updateAttributes({ html: value });
+		},
+		[updateAttributes],
+	);
+
+	const handleChange = React.useCallback(
+		(e: React.ChangeEvent<HTMLTextAreaElement>) => {
+			setDraft(e.target.value);
+			commitHtml(e.target.value);
+		},
+		[commitHtml],
+	);
+
+	return (
+		<NodeViewWrapper
+			className={cn(
+				"html-block relative my-3",
+				selected && "ring-2 ring-kumo-brand ring-offset-2 rounded-lg",
+			)}
+			contentEditable={false}
+			data-drag-handle
+		>
+			<div className="relative group">
+				{/* Drag handle */}
+				<div
+					className={cn(
+						"absolute -start-8 top-1/2 -translate-y-1/2 opacity-0 group-hover:opacity-100 transition-opacity cursor-grab active:cursor-grabbing",
+						selected && "opacity-100",
+					)}
+					data-drag-handle
+				>
+					<DotsSixVertical className="h-5 w-5 text-kumo-subtle/50" />
+				</div>
+
+				{/* Main block */}
+				<div
+					className={cn(
+						"rounded-lg border bg-kumo-base transition-colors overflow-hidden",
+						selected ? "border-kumo-brand/50 bg-kumo-tint/30" : "hover:border-kumo-line",
+					)}
+				>
+					{/* Header */}
+					<div className="flex items-center gap-3 px-4 py-3">
+						<div className="flex-shrink-0 w-10 h-10 rounded-lg bg-kumo-tint flex items-center justify-center text-kumo-subtle">
+							<BracketsAngle className="h-5 w-5" />
+						</div>
+
+						<div className="flex-1 min-w-0">
+							<div className="text-sm font-medium">{t`HTML`}</div>
+						</div>
+
+						{/* Actions */}
+						<div
+							className={cn(
+								"flex items-center gap-1 transition-opacity",
+								selected ? "opacity-100" : "opacity-0 group-hover:opacity-100",
+							)}
+						>
+							<Button
+								type="button"
+								variant="ghost"
+								shape="square"
+								className="h-8 w-8 text-kumo-danger hover:text-kumo-danger hover:bg-kumo-danger/10"
+								onClick={() => deleteNode()}
+								title={t`Delete`}
+								aria-label={t`Delete HTML block`}
+							>
+								<Trash className="h-4 w-4" />
+							</Button>
+						</div>
+					</div>
+
+					{/* Content area */}
+					<div className="px-4 pb-4">
+						<textarea
+							ref={textareaRef}
+							value={draft}
+							onChange={handleChange}
+							placeholder={t`Enter HTML...`}
+							className="w-full min-h-[100px] resize-y rounded-md border bg-kumo-overlay p-3 font-mono text-sm text-kumo-strong placeholder:text-kumo-subtle focus:outline-none focus:ring-2 focus:ring-kumo-brand"
+							spellCheck={false}
+							aria-label={t`HTML source`}
+						/>
+					</div>
+				</div>
+			</div>
+		</NodeViewWrapper>
+	);
+}
+
+// ---------------------------------------------------------------------------
+// TipTap Extension
+// ---------------------------------------------------------------------------
+
+/**
+ * TipTap extension: first-class HTML block.
+ *
+ * An atom node that stores raw HTML in a `html` attribute. Round-trips
+ * through Portable Text as `{ _type: "htmlBlock", _key, html }`.
+ */
+export const HtmlBlockExtension = Node.create({
+	name: "htmlBlock",
+	group: "block",
+	atom: true,
+	draggable: true,
+	selectable: true,
+
+	addAttributes() {
+		return {
+			html: {
+				default: "",
+			},
+		};
+	},
+
+	parseHTML() {
+		return [
+			{
+				tag: "div[data-html-block]",
+			},
+		];
+	},
+
+	renderHTML({ HTMLAttributes }) {
+		return ["div", mergeAttributes(HTMLAttributes, { "data-html-block": "" })];
+	},
+
+	addNodeView() {
+		return ReactNodeViewRenderer(HtmlBlockNodeView);
+	},
+
+	addKeyboardShortcuts() {
+		return {
+			Backspace: () => {
+				const { selection } = this.editor.state;
+				const node = this.editor.state.doc.nodeAt(selection.from);
+				if (node?.type.name === "htmlBlock") {
+					this.editor.commands.deleteSelection();
+					return true;
+				}
+				return false;
+			},
+			Delete: () => {
+				const { selection } = this.editor.state;
+				const node = this.editor.state.doc.nodeAt(selection.from);
+				if (node?.type.name === "htmlBlock") {
+					this.editor.commands.deleteSelection();
+					return true;
+				}
+				return false;
+			},
+		};
+	},
+});
diff --git a/packages/core/src/components/InlinePortableTextEditor.tsx b/packages/core/src/components/InlinePortableTextEditor.tsx
index 4b8b7efb7..f4d9efca0 100644
--- a/packages/core/src/components/InlinePortableTextEditor.tsx
+++ b/packages/core/src/components/InlinePortableTextEditor.tsx
@@ -183,6 +183,14 @@ function convertPMNode(node: PMNode): PTBlock | PTBlock[] | null {
 				language: attrStrOpt(node.attrs, "language"),
 			};
 		}
+		case "htmlBlock": {
+			const rawHtml = node.attrs?.html;
+			return {
+				_type: "htmlBlock",
+				_key: k(),
+				html: typeof rawHtml === "string" ? rawHtml : "",
+			};
+		}
 		case "image": {
 			const provider = attrStrOpt(node.attrs, "provider");
 			return {
@@ -391,6 +399,13 @@ function convertPTBlock(block: PTBlock): JSONContent | null {
 	if (block._type === "break") {
 		return { type: "horizontalRule" };
 	}
+	if (block._type === "htmlBlock") {
+		const hb = block as PTBlock & { html?: string };
+		return {
+			type: "htmlBlock",
+			attrs: { html: hb.html || "" },
+		};
+	}
 	if (block._type === "image") {
 		const ib = block as PTBlock & {
 			asset?: { _ref?: string; url?: string; provider?: string };
@@ -731,6 +746,21 @@ const slashCommands: SlashCommandItem[] = [
 			editor.chain().focus().deleteRange(range).toggleCodeBlock().run();
 		},
 	},
+	{
+		id: "htmlBlock",
+		title: "HTML",
+		description: "Insert raw HTML",
+		icon: "< >",
+		aliases: ["html", "raw", "markup"],
+		command: ({ editor, range }) => {
+			editor
+				.chain()
+				.focus()
+				.deleteRange(range)
+				.insertContent({ type: "htmlBlock", attrs: { html: "" } })
+				.run();
+		},
+	},
 	{
 		id: "divider",
 		title: "Divider",
@@ -771,6 +801,44 @@ const initialSlashMenuState: SlashMenuState = {
 	range: null,
 };
 
+/**
+ * Minimal `htmlBlock` TipTap node for the inline (visual-editing) editor.
+ *
+ * Like PluginBlockNode below, this renders as a read-only placeholder so the
+ * block's data is preserved across edits in the visual editor. Full editing
+ * (textarea + preview) is only available in the admin editor.
+ */
+const HtmlBlockNode = Node.create({
+	name: "htmlBlock",
+	group: "block",
+	atom: true,
+	selectable: true,
+	draggable: true,
+
+	addAttributes() {
+		const noDom = { rendered: false, parseHTML: () => null };
+		return {
+			html: { default: "", ...noDom },
+		};
+	},
+
+	parseHTML() {
+		return [{ tag: 'div[data-emdash-html-block="true"]' }];
+	},
+
+	renderHTML({ HTMLAttributes }) {
+		return [
+			"div",
+			mergeAttributes(HTMLAttributes, {
+				"data-emdash-html-block": "true",
+				class: "emdash-plugin-block-placeholder",
+				contenteditable: "false",
+			}),
+			"HTML block (edit in admin)",
+		];
+	},
+});
+
 /**
  * Minimal `pluginBlock` TipTap node for the inline (visual-editing) editor.
  *
@@ -1801,6 +1869,7 @@ export function InlinePortableTextEditor({
 				mode: "all",
 			}),
 			Typography,
+			HtmlBlockNode,
 			PluginBlockNode,
 			slashCommandsExtension,
 		],
diff --git a/packages/core/src/content/converters/portable-text-to-prosemirror.ts b/packages/core/src/content/converters/portable-text-to-prosemirror.ts
index 24fc132b9..d08f11b90 100644
--- a/packages/core/src/content/converters/portable-text-to-prosemirror.ts
+++ b/packages/core/src/content/converters/portable-text-to-prosemirror.ts
@@ -111,6 +111,13 @@ function convertBlock(block: PortableTextBlock): ProseMirrorNode | null {
 	if (isCodeBlock(block)) {
 		return convertCodeBlock(block);
 	}
+	if (block._type === "htmlBlock") {
+		const hb = block as PortableTextBlock & { html?: string };
+		return {
+			type: "htmlBlock",
+			attrs: { html: hb.html || "" },
+		};
+	}
 	if (block._type === "break") {
 		return { type: "horizontalRule" };
 	}
diff --git a/packages/core/src/content/converters/prosemirror-to-portable-text.ts b/packages/core/src/content/converters/prosemirror-to-portable-text.ts
index 055200b93..918cb3d12 100644
--- a/packages/core/src/content/converters/prosemirror-to-portable-text.ts
+++ b/packages/core/src/content/converters/prosemirror-to-portable-text.ts
@@ -14,6 +14,7 @@ import type {
 	PortableTextMarkDef,
 	PortableTextImageBlock,
 	PortableTextCodeBlock,
+	PortableTextHtmlBlock,
 } from "./types.js";
 
 /**
@@ -70,6 +71,9 @@ function convertNode(node: ProseMirrorNode): PortableTextBlock | PortableTextBlo
 		case "codeBlock":
 			return convertCodeBlock(node);
 
+		case "htmlBlock":
+			return convertHtmlBlock(node);
+
 		case "image":
 			return convertImage(node);
 
@@ -268,6 +272,18 @@ function convertCodeBlock(node: ProseMirrorNode): PortableTextCodeBlock {
 	};
 }
 
+/**
+ * Convert HTML block to Portable Text
+ */
+function convertHtmlBlock(node: ProseMirrorNode): PortableTextHtmlBlock {
+	const rawHtml = node.attrs?.html;
+	return {
+		_type: "htmlBlock",
+		_key: generateKey(),
+		html: typeof rawHtml === "string" ? rawHtml : "",
+	};
+}
+
 /**
  * Convert image to Portable Text
  */
diff --git a/packages/core/src/content/converters/types.ts b/packages/core/src/content/converters/types.ts
index aed1e7b04..9ff32abdf 100644
--- a/packages/core/src/content/converters/types.ts
+++ b/packages/core/src/content/converters/types.ts
@@ -80,6 +80,15 @@ export interface PortableTextCodeBlock {
 	filename?: string;
 }
 
+/**
+ * HTML block (raw HTML content)
+ */
+export interface PortableTextHtmlBlock {
+	_type: "htmlBlock";
+	_key: string;
+	html: string;
+}
+
 /**
  * Unknown/custom block (preserved for plugin compatibility)
  */
@@ -96,6 +105,7 @@ export type PortableTextBlock =
 	| PortableTextTextBlock
 	| PortableTextImageBlock
 	| PortableTextCodeBlock
+	| PortableTextHtmlBlock
 	| PortableTextUnknownBlock;
 
 /**
diff --git a/packages/core/src/index.ts b/packages/core/src/index.ts
index d70ad0bd2..b6fdb5468 100644
--- a/packages/core/src/index.ts
+++ b/packages/core/src/index.ts
@@ -96,6 +96,7 @@ export type {
 	PortableTextTextBlock,
 	PortableTextImageBlock,
 	PortableTextCodeBlock,
+	PortableTextHtmlBlock,
 	PortableTextUnknownBlock,
 	ProseMirrorMark,
 	ProseMirrorNode,
diff --git a/packages/core/tests/unit/converters/html-block-round-trip.test.ts b/packages/core/tests/unit/converters/html-block-round-trip.test.ts
new file mode 100644
index 000000000..40067185a
--- /dev/null
+++ b/packages/core/tests/unit/converters/html-block-round-trip.test.ts
@@ -0,0 +1,87 @@
+import { describe, it, expect } from "vitest";
+
+import { portableTextToProsemirror } from "../../../src/content/converters/portable-text-to-prosemirror.js";
+import { prosemirrorToPortableText } from "../../../src/content/converters/prosemirror-to-portable-text.js";
+import type { PortableTextHtmlBlock } from "../../../src/content/converters/types.js";
+
+describe("HTML block round-trip (core converters)", () => {
+	it("preserves html content through PT → PM → PT", () => {
+		const htmlBlock: PortableTextHtmlBlock = {
+			_type: "htmlBlock",
+			_key: "html001",
+			html: '<div class="callout"><p>Hello <strong>world</strong></p></div>',
+		};
+
+		// PT → PM
+		const pm = portableTextToProsemirror([htmlBlock]);
+		const node = pm.content[0];
+
+		expect(node).toBeDefined();
+		expect(node.type).toBe("htmlBlock");
+		expect(node.attrs?.html).toBe(htmlBlock.html);
+
+		// PM → PT
+		const pt = prosemirrorToPortableText(pm);
+		const restored = pt[0] as PortableTextHtmlBlock;
+
+		expect(restored._type).toBe("htmlBlock");
+		expect(restored.html).toBe(htmlBlock.html);
+		expect(restored._key).toBeDefined();
+	});
+
+	it("handles empty html content", () => {
+		const emptyBlock: PortableTextHtmlBlock = {
+			_type: "htmlBlock",
+			_key: "html002",
+			html: "",
+		};
+
+		const pm = portableTextToProsemirror([emptyBlock]);
+		const node = pm.content[0];
+
+		expect(node).toBeDefined();
+		expect(node.type).toBe("htmlBlock");
+		expect(node.attrs?.html).toBe("");
+
+		const pt = prosemirrorToPortableText(pm);
+		const restored = pt[0] as PortableTextHtmlBlock;
+
+		expect(restored._type).toBe("htmlBlock");
+		expect(restored.html).toBe("");
+	});
+
+	it("preserves html blocks among other block types", () => {
+		const blocks = [
+			{
+				_type: "block" as const,
+				_key: "txt001",
+				style: "normal" as const,
+				children: [{ _type: "span" as const, _key: "s1", text: "Before" }],
+			},
+			{
+				_type: "htmlBlock" as const,
+				_key: "html003",
+				html: "<hr><p>Injected</p>",
+			},
+			{
+				_type: "block" as const,
+				_key: "txt002",
+				style: "normal" as const,
+				children: [{ _type: "span" as const, _key: "s2", text: "After" }],
+			},
+		];
+
+		const pm = portableTextToProsemirror(blocks);
+		expect(pm.content).toHaveLength(3);
+		expect(pm.content[0].type).toBe("paragraph");
+		expect(pm.content[1].type).toBe("htmlBlock");
+		expect(pm.content[2].type).toBe("paragraph");
+
+		const pt = prosemirrorToPortableText(pm);
+		expect(pt).toHaveLength(3);
+		expect(pt[0]._type).toBe("block");
+		expect(pt[1]._type).toBe("htmlBlock");
+		expect((pt[1] as PortableTextHtmlBlock).html).toBe("<hr><p>Injected</p>");
+		expect(pt[2]._type).toBe("block");
+	});
+});