diff --git a/CHANGELOG.md b/CHANGELOG.md
index 259d7da..111f519 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,7 @@
   * `TypeNullIn30`: detect `type: "null"` usage in 3.0 documents (3.1 primitive)
   * `WebhooksIn30`: detect root-level `webhooks` usage in 3.0 documents (3.1 addition)
   * `ConstIn30`: detect `const` usage in 3.0 documents (3.1 addition)
+  * `DynamicRefIn30`: detect `$dynamicRef` usage in 3.0 documents (3.1 addition)
 * support 3.1-style numeric `exclusiveMinimum` / `exclusiveMaximum` in value validation (standalone bound, not a Boolean modifier on `minimum` / `maximum`)
 * support `type: "null"` (3.1 primitive) in value validation
 * support root-level `webhooks` (OpenAPI 3.1) in the parse layer
diff --git a/lib/openapi_parser/spec_validator.rb b/lib/openapi_parser/spec_validator.rb
index 9a8e7c6..f7c87f7 100644
--- a/lib/openapi_parser/spec_validator.rb
+++ b/lib/openapi_parser/spec_validator.rb
@@ -10,6 +10,7 @@
 require_relative 'spec_validator/rules/type_null_in_30'
 require_relative 'spec_validator/rules/webhooks_in_30'
 require_relative 'spec_validator/rules/const_in_30'
+require_relative 'spec_validator/rules/dynamic_ref_in_30'
 
 module OpenAPIParser
   class SpecViolationError < OpenAPIError
@@ -67,6 +68,7 @@ def rules
           Rules::TypeNullIn30,
           Rules::WebhooksIn30,
           Rules::ConstIn30,
+          Rules::DynamicRefIn30,
         ]
       end
   end
diff --git a/lib/openapi_parser/spec_validator/rules/dynamic_ref_in_30.rb b/lib/openapi_parser/spec_validator/rules/dynamic_ref_in_30.rb
new file mode 100644
index 0000000..34b7e62
--- /dev/null
+++ b/lib/openapi_parser/spec_validator/rules/dynamic_ref_in_30.rb
@@ -0,0 +1,25 @@
+module OpenAPIParser
+  class SpecValidator
+    module Rules
+      # `$dynamicRef` is a JSON Schema 2020-12 referencing mechanism that
+      # 3.1 adopted. 3.0 does not recognize it. The parse layer keeps the
+      # value as raw schema data; this rule reports the version mismatch.
+      class DynamicRefIn30 < Rule
+        def check(root)
+          return [] unless version == :v3_0
+
+          violations = []
+          each_schema(root) do |schema|
+            next unless schema.raw_schema.is_a?(Hash) && schema.raw_schema.key?('$dynamicRef')
+
+            violations << violation(
+              path: schema.object_reference,
+              message: '`$dynamicRef` is a 3.1 addition (from JSON Schema 2020-12); 3.0 only knows `$ref`',
+            )
+          end
+          violations
+        end
+      end
+    end
+  end
+end
diff --git a/sig/openapi_parser/spec_validator.rbs b/sig/openapi_parser/spec_validator.rbs
index 10250d1..c4f37bc 100644
--- a/sig/openapi_parser/spec_validator.rbs
+++ b/sig/openapi_parser/spec_validator.rbs
@@ -76,6 +76,10 @@ module OpenAPIParser
       class ConstIn30 < Rule
         def check: (OpenAPIParser::Schemas::OpenAPI root) -> Array[SpecValidator::SpecViolation]
       end
+
+      class DynamicRefIn30 < Rule
+        def check: (OpenAPIParser::Schemas::OpenAPI root) -> Array[SpecValidator::SpecViolation]
+      end
     end
   end
 
diff --git a/spec/data/openapi_3_1/dynamic_ref_30.yaml b/spec/data/openapi_3_1/dynamic_ref_30.yaml
new file mode 100644
index 0000000..1d1a38f
--- /dev/null
+++ b/spec/data/openapi_3_1/dynamic_ref_30.yaml
@@ -0,0 +1,26 @@
+openapi: 3.0.3
+info:
+  title: Tree API
+  version: '1.0'
+paths:
+  /trees:
+    get:
+      summary: Fetch a tree
+      responses:
+        '200':
+          description: OK
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/Node'
+components:
+  schemas:
+    Node:
+      type: object
+      properties:
+        children:
+          type: array
+          # `$dynamicRef` is a JSON Schema 2020-12 dynamic referencing keyword
+          # adopted by 3.1; 3.0 only knows `$ref`, so this is a spec violation.
+          items:
+            $dynamicRef: '#node'
diff --git a/spec/data/openapi_3_1/dynamic_ref_31.yaml b/spec/data/openapi_3_1/dynamic_ref_31.yaml
new file mode 100644
index 0000000..5d42534
--- /dev/null
+++ b/spec/data/openapi_3_1/dynamic_ref_31.yaml
@@ -0,0 +1,26 @@
+openapi: 3.1.0
+info:
+  title: Tree API
+  version: '1.0'
+paths:
+  /trees:
+    get:
+      summary: Fetch a tree
+      responses:
+        '200':
+          description: OK
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/Node'
+components:
+  schemas:
+    Node:
+      type: object
+      properties:
+        children:
+          type: array
+          # `$dynamicRef` is legitimate under 3.1 (JSON Schema 2020-12), so no
+          # violation is expected here.
+          items:
+            $dynamicRef: '#node'
diff --git a/spec/openapi_parser/spec_validator/integration_3_1_spec.rb b/spec/openapi_parser/spec_validator/integration_3_1_spec.rb
index 78e6c14..7fc4892 100644
--- a/spec/openapi_parser/spec_validator/integration_3_1_spec.rb
+++ b/spec/openapi_parser/spec_validator/integration_3_1_spec.rb
@@ -184,4 +184,18 @@ def expect_clean(file)
       expect_clean('const_31.yaml')
     end
   end
+
+  describe '$dynamicRef (JSON Schema 2020-12 referencing new in 3.1)' do
+    it 'warns on the version-mismatched document under :warn' do
+      expect_mismatch_warns('dynamic_ref_30.yaml', [:dynamic_ref_in30])
+    end
+
+    it 'raises SpecViolationError on the version-mismatched document under :raise' do
+      expect_mismatch_raises('dynamic_ref_30.yaml', [:dynamic_ref_in30])
+    end
+
+    it 'stays clean on the correctly-versioned document' do
+      expect_clean('dynamic_ref_31.yaml')
+    end
+  end
 end
diff --git a/spec/openapi_parser/spec_validator/rules/dynamic_ref_in_30_spec.rb b/spec/openapi_parser/spec_validator/rules/dynamic_ref_in_30_spec.rb
new file mode 100644
index 0000000..c9949b4
--- /dev/null
+++ b/spec/openapi_parser/spec_validator/rules/dynamic_ref_in_30_spec.rb
@@ -0,0 +1,64 @@
+require_relative '../../../spec_helper'
+
+RSpec.describe 'OpenAPIParser::SpecValidator::Rules::DynamicRefIn30' do
+  def base_doc(openapi_version_string, sample_schema)
+    {
+      'openapi' => openapi_version_string,
+      'info' => { 'title' => 'test', 'version' => '1.0' },
+      'paths' => {},
+      'components' => { 'schemas' => { 'Sample' => sample_schema } },
+    }
+  end
+
+  def doc_with_dynamic_ref(openapi_version_string)
+    raw = base_doc(openapi_version_string, { '$dynamicRef' => '#meta' })
+    OpenAPIParser.parse(raw, strict_reference_validation: false)
+  end
+
+  def doc_without_dynamic_ref(openapi_version_string)
+    raw = base_doc(openapi_version_string, { 'type' => 'string' })
+    OpenAPIParser.parse(raw, strict_reference_validation: false)
+  end
+
+  def run_rule_for(root)
+    OpenAPIParser::SpecValidator::Rules::DynamicRefIn30.new(root.openapi_version).check(root)
+  end
+
+  context 'with a 3.1 document using $dynamicRef' do
+    it 'reports no violation' do
+      root = doc_with_dynamic_ref('3.1.0')
+      expect(run_rule_for(root)).to eq []
+    end
+  end
+
+  context 'with a 3.1 document without $dynamicRef' do
+    it 'reports no violation' do
+      root = doc_without_dynamic_ref('3.1.0')
+      expect(run_rule_for(root)).to eq []
+    end
+  end
+
+  context 'with a 3.0 document using $dynamicRef' do
+    it 'reports one violation pointing at the offending schema' do
+      root = doc_with_dynamic_ref('3.0.0')
+      violations = run_rule_for(root)
+      expect(violations.size).to eq 1
+      expect(violations.first.path).to eq '#/components/schemas/Sample'
+      expect(violations.first.rule_name).to eq :dynamic_ref_in30
+    end
+  end
+
+  context 'with a 3.0 document without $dynamicRef' do
+    it 'reports no violation' do
+      root = doc_without_dynamic_ref('3.0.0')
+      expect(run_rule_for(root)).to eq []
+    end
+  end
+
+  context 'with an :unknown version document' do
+    it 'reports no violation (rule skipped)' do
+      root = doc_with_dynamic_ref('4.0.0')
+      expect(run_rule_for(root)).to eq []
+    end
+  end
+end