diff --git a/book/src/generated/lang-support.md b/book/src/generated/lang-support.md
index 4dca81047..fa7b6edd3 100644
--- a/book/src/generated/lang-support.md
+++ b/book/src/generated/lang-support.md
@@ -77,6 +77,7 @@
 | make | ✓ |  |  |  |
 | markdown | ✓ |  |  | `marksman` |
 | markdown.inline | ✓ |  |  |  |
+| mermaid | ✓ |  |  |  |
 | meson | ✓ |  | ✓ |  |
 | mint |  |  |  | `mint` |
 | nickel | ✓ |  | ✓ | `nls` |
diff --git a/languages.toml b/languages.toml
index e6bc344cc..e28476d31 100644
--- a/languages.toml
+++ b/languages.toml
@@ -2043,3 +2043,16 @@ grammar = "qmljs"
 [[grammar]]
 name = "qmljs"
 source = { git = "https://github.com/yuja/tree-sitter-qmljs", rev = "0b2b25bcaa7d4925d5f0dda16f6a99c588a437f1" }
+
+[[language]]
+name = "mermaid"
+scope = "source.mermaid"
+injection-regex = "mermaid"
+file-types = ["mermaid"]
+roots = []
+comment-token = "%%"
+indent = { tab-width = 4, unit = "    " }
+
+[[grammar]]
+name = "mermaid"
+source = { git = "https://github.com/monaqa/tree-sitter-mermaid", rev = "d787c66276e7e95899230539f556e8b83ee16f6d" }
diff --git a/runtime/queries/mermaid/highlights.scm b/runtime/queries/mermaid/highlights.scm
new file mode 100644
index 000000000..b546d39f2
--- /dev/null
+++ b/runtime/queries/mermaid/highlights.scm
@@ -0,0 +1,187 @@
+[
+ "sequenceDiagram"
+ "classDiagram"
+ "classDiagram-v2"
+ "stateDiagram"
+ "stateDiagram-v2"
+ "gantt"
+ "pie"
+ "flowchart"
+ "erdiagram"
+
+ "participant"
+ "as"
+ "activate"
+ "deactivate"
+ "note "
+ "over"
+ "link"
+ "links"
+ ; "left of"
+ ; "right of"
+ "properties"
+ "details"
+ "title"
+ "loop"
+ "rect"
+ "opt"
+ "alt"
+ "else"
+ "par"
+ "and"
+ "end"
+ (sequence_stmt_autonumber)
+ (note_placement_left)
+ (note_placement_right)
+
+ "class"
+
+ "state "
+
+ "dateformat"
+ "inclusiveenddates"
+ "topaxis"
+ "axisformat"
+ "includes"
+ "excludes"
+ "todaymarker"
+ "title"
+ "section"
+
+ "direction"
+ "subgraph"
+
+ ] @keyword
+
+[
+ (comment)
+ ] @comment
+
+(flow_vertex_id) @type
+(flow_arrow_text) @label
+(flow_text_literal) @string
+ 
+[
+ ":"
+ (sequence_signal_plus_sign)
+ (sequence_signal_minus_sign)
+
+ (class_visibility_public)
+ (class_visibility_private)
+ (class_visibility_protected)
+ (class_visibility_internal)
+
+ (state_division)
+ ] @punctuation.delimiter
+
+[
+ "("
+ ")"
+ "{"
+ "}"
+ ] @punctuation.bracket
+
+[
+ "-->"
+ (solid_arrow)
+ (dotted_arrow)
+ (solid_open_arrow)
+ (dotted_open_arrow)
+ (solid_cross)
+ (dotted_cross)
+ (solid_point)
+ (dotted_point)
+ ] @operator
+
+[
+ (class_reltype_aggregation)
+ (class_reltype_extension)
+ (class_reltype_composition)
+ (class_reltype_dependency)
+ (class_linetype_solid)
+ (class_linetype_dotted)
+ "&"
+ ] @operator
+
+(sequence_actor) @variable
+(sequence_text) @string
+
+(class_name) @type
+(class_label) @string
+(class_method_line) @function.method
+
+(state_name) @variable
+
+(gantt_section) @markup.heading
+(gantt_task_text) @variable.builtin
+(gantt_task_data) @string
+
+[
+ (class_annotation_line)
+ (class_stmt_annotation)
+ (class_generics)
+
+ (state_annotation_fork)
+ (state_annotation_join)
+ (state_annotation_choice)
+ ] @type
+
+(directive) @keyword.directive
+
+(pie_label) @string
+(pie_value) @constant.numeric
+
+[
+(flowchart_direction_lr)
+(flowchart_direction_rl)
+(flowchart_direction_tb)
+(flowchart_direction_bt)
+ ] @constant
+
+(flow_vertex_id) @variable
+
+[
+ (flow_link_arrow)
+ (flow_link_arrow_start)
+ ] @operator
+
+(flow_link_arrowtext "|" @punctuation.bracket)
+
+(flow_vertex_square        [ "[" "]" ]   @punctuation.bracket )
+(flow_vertex_circle        ["((" "))"]   @punctuation.bracket )
+(flow_vertex_ellipse       ["(-" "-)"]   @punctuation.bracket )
+(flow_vertex_stadium       ["([" "])"]   @punctuation.bracket )
+(flow_vertex_subroutine    ["[[" "]]"]   @punctuation.bracket )
+(flow_vertex_rect          ["[|" "|]"]   @punctuation.bracket )
+(flow_vertex_cylinder      ["[(" ")]"]   @punctuation.bracket )
+(flow_vertex_round         ["(" ")"]     @punctuation.bracket )
+(flow_vertex_diamond       ["{" "}"]     @punctuation.bracket )
+(flow_vertex_hexagon       ["{{" "}}"]   @punctuation.bracket )
+(flow_vertex_odd           [">" "]"]     @punctuation.bracket )
+(flow_vertex_trapezoid     ["[/" "\\]"]  @punctuation.bracket )
+(flow_vertex_inv_trapezoid ["[\\" "/]"]  @punctuation.bracket )
+(flow_vertex_leanright     ["[/" "/]"]   @punctuation.bracket )
+(flow_vertex_leanleft      ["[\\" "\\]"] @punctuation.bracket )
+
+(flow_stmt_subgraph ["[" "]"] @punctuation.bracket )
+
+[
+ (er_cardinarity_zero_or_one)
+ (er_cardinarity_zero_or_more)
+ (er_cardinarity_one_or_more)
+ (er_cardinarity_only_one)
+ (er_reltype_non_identifying)
+ (er_reltype_identifying)
+ ] @operator
+
+(er_entity_name) @variable
+
+(er_attribute_type) @type
+(er_attribute_name) @variable
+
+[
+ (er_attribute_key_type_pk)
+ (er_attribute_key_type_fk)
+ ] @keyword
+
+(er_attribute_comment) @string