diff --git a/plugin/scripts/lib/md-checks.mjs b/plugin/scripts/lib/md-checks.mjs
index 5cf5759..3502066 100644
--- a/plugin/scripts/lib/md-checks.mjs
+++ b/plugin/scripts/lib/md-checks.mjs
@@ -27,6 +27,9 @@
 //   ref-undefined       full/collapsed reference [text][label] with no
 //                       definition (renders as literal brackets on GitHub)
 //   def-orphan          a [label]: definition no reference ever uses
+//   image-alt-missing   image with empty or absent alt text — screen readers
+//                       announce "image" with no description, search engines
+//                       cannot index content (MD045 class, WCAG 1.1.1)
 //   bare-url            a raw http(s)/www URL in prose text (GFM auto-links
 //                       it, CommonMark does not; MD034 class — style signal)
 //   doc-too-large       pre-parse short-circuit: input over MAX_DOC_BYTES is
@@ -246,6 +249,19 @@ export function checkDocument(src, opts = {}) {
     if (node.type === 'link' || node.type === 'image' || node.type === 'definition') checkTarget(node, node.url);
   });
 
+  // ---- images: alt text -------------------------------------------------------
+  // MD045 / WCAG 1.1.1: every image needs a non-empty alt. Without it a screen
+  // reader says "image" with no description, and search engines cannot index the
+  // content. Both inline images (![alt](url)) and reference images (![alt][ref])
+  // are checked — the AST carries the alt field on both node types.
+  walk(root, (node) => {
+    if (node.type !== 'image' && node.type !== 'imageReference') return;
+    const alt = (node.alt || '').trim();
+    if (!alt) {
+      add('image-alt-missing', node, `image has no alt text — screen readers and search engines cannot describe it (MD045)`);
+    }
+  });
+
   // ---- tables ----------------------------------------------------------------
   walk(root, (node) => {
     if (node.type !== 'table' || !node.children.length) return;
diff --git a/plugin/skills/doc-structure/SKILL.md b/plugin/skills/doc-structure/SKILL.md
index e27a13c..8cc75ad 100644
--- a/plugin/skills/doc-structure/SKILL.md
+++ b/plugin/skills/doc-structure/SKILL.md
@@ -36,6 +36,7 @@ Scan markdown docs for structural breakage. Report CONFIRMED findings. Fix on re
 | table-ragged | row with MORE cells than the header (GitHub silently drops them) |
 | ref-undefined | \[text]\[label] with no definition (renders as literal brackets) |
 | def-orphan | definition never referenced |
+| image-alt-missing | image with empty or absent alt text — inaccessible to screen readers, invisible to search engines (MD045 / WCAG 1.1.1) |
 | bare-url | raw URL in prose (MD034 class) |
 | doc-unreadable | binary/corrupted input (NUL byte sniffed) — refused before parsing, never a false "0 findings" clean bill |
 
diff --git a/plugin/skills/doc-structure/lib/md-checks.mjs b/plugin/skills/doc-structure/lib/md-checks.mjs
index 5cf5759..3502066 100644
--- a/plugin/skills/doc-structure/lib/md-checks.mjs
+++ b/plugin/skills/doc-structure/lib/md-checks.mjs
@@ -27,6 +27,9 @@
 //   ref-undefined       full/collapsed reference [text][label] with no
 //                       definition (renders as literal brackets on GitHub)
 //   def-orphan          a [label]: definition no reference ever uses
+//   image-alt-missing   image with empty or absent alt text — screen readers
+//                       announce "image" with no description, search engines
+//                       cannot index content (MD045 class, WCAG 1.1.1)
 //   bare-url            a raw http(s)/www URL in prose text (GFM auto-links
 //                       it, CommonMark does not; MD034 class — style signal)
 //   doc-too-large       pre-parse short-circuit: input over MAX_DOC_BYTES is
@@ -246,6 +249,19 @@ export function checkDocument(src, opts = {}) {
     if (node.type === 'link' || node.type === 'image' || node.type === 'definition') checkTarget(node, node.url);
   });
 
+  // ---- images: alt text -------------------------------------------------------
+  // MD045 / WCAG 1.1.1: every image needs a non-empty alt. Without it a screen
+  // reader says "image" with no description, and search engines cannot index the
+  // content. Both inline images (![alt](url)) and reference images (![alt][ref])
+  // are checked — the AST carries the alt field on both node types.
+  walk(root, (node) => {
+    if (node.type !== 'image' && node.type !== 'imageReference') return;
+    const alt = (node.alt || '').trim();
+    if (!alt) {
+      add('image-alt-missing', node, `image has no alt text — screen readers and search engines cannot describe it (MD045)`);
+    }
+  });
+
   // ---- tables ----------------------------------------------------------------
   walk(root, (node) => {
     if (node.type !== 'table' || !node.children.length) return;
diff --git a/scripts/fixtures/defects-structure.md b/scripts/fixtures/defects-structure.md
index 0bd49d5..d510736 100644
--- a/scripts/fixtures/defects-structure.md
+++ b/scripts/fixtures/defects-structure.md
@@ -31,3 +31,5 @@ Bare URL: https://example.com/dangling in prose.
 Some instructions.
 
 ## Setup
+
+![](./img/no-alt.png)
diff --git a/scripts/lib/md-checks.mjs b/scripts/lib/md-checks.mjs
index 5cf5759..3502066 100644
--- a/scripts/lib/md-checks.mjs
+++ b/scripts/lib/md-checks.mjs
@@ -27,6 +27,9 @@
 //   ref-undefined       full/collapsed reference [text][label] with no
 //                       definition (renders as literal brackets on GitHub)
 //   def-orphan          a [label]: definition no reference ever uses
+//   image-alt-missing   image with empty or absent alt text — screen readers
+//                       announce "image" with no description, search engines
+//                       cannot index content (MD045 class, WCAG 1.1.1)
 //   bare-url            a raw http(s)/www URL in prose text (GFM auto-links
 //                       it, CommonMark does not; MD034 class — style signal)
 //   doc-too-large       pre-parse short-circuit: input over MAX_DOC_BYTES is
@@ -246,6 +249,19 @@ export function checkDocument(src, opts = {}) {
     if (node.type === 'link' || node.type === 'image' || node.type === 'definition') checkTarget(node, node.url);
   });
 
+  // ---- images: alt text -------------------------------------------------------
+  // MD045 / WCAG 1.1.1: every image needs a non-empty alt. Without it a screen
+  // reader says "image" with no description, and search engines cannot index the
+  // content. Both inline images (![alt](url)) and reference images (![alt][ref])
+  // are checked — the AST carries the alt field on both node types.
+  walk(root, (node) => {
+    if (node.type !== 'image' && node.type !== 'imageReference') return;
+    const alt = (node.alt || '').trim();
+    if (!alt) {
+      add('image-alt-missing', node, `image has no alt text — screen readers and search engines cannot describe it (MD045)`);
+    }
+  });
+
   // ---- tables ----------------------------------------------------------------
   walk(root, (node) => {
     if (node.type !== 'table' || !node.children.length) return;
diff --git a/scripts/lib/md-checks.test.mjs b/scripts/lib/md-checks.test.mjs
index 1215541..86dd825 100644
--- a/scripts/lib/md-checks.test.mjs
+++ b/scripts/lib/md-checks.test.mjs
@@ -31,7 +31,9 @@ test('defects-structure.md: every planted defect found — exact check ids and l
     'def-orphan@27',
     'file-missing@11', // ./no-such-file.md
     'file-missing@13', // dead image
+    'file-missing@35', // no-alt image target also missing
     'heading-duplicate@33', // second "## Setup" — anchor silently points to first
+    'image-alt-missing@35', // ![](./img/no-alt.png) — no alt text
     'heading-multiple-h1@5',
     'heading-skip@3',
     'ref-undefined@23',
diff --git a/skills/doc-structure/SKILL.md b/skills/doc-structure/SKILL.md
index e27a13c..8cc75ad 100644
--- a/skills/doc-structure/SKILL.md
+++ b/skills/doc-structure/SKILL.md
@@ -36,6 +36,7 @@ Scan markdown docs for structural breakage. Report CONFIRMED findings. Fix on re
 | table-ragged | row with MORE cells than the header (GitHub silently drops them) |
 | ref-undefined | \[text]\[label] with no definition (renders as literal brackets) |
 | def-orphan | definition never referenced |
+| image-alt-missing | image with empty or absent alt text — inaccessible to screen readers, invisible to search engines (MD045 / WCAG 1.1.1) |
 | bare-url | raw URL in prose (MD034 class) |
 | doc-unreadable | binary/corrupted input (NUL byte sniffed) — refused before parsing, never a false "0 findings" clean bill |