diff --git a/src/tint/writer/hlsl/generator_impl.cc b/src/tint/writer/hlsl/generator_impl.cc
index b7020f6..9a66118 100644
--- a/src/tint/writer/hlsl/generator_impl.cc
+++ b/src/tint/writer/hlsl/generator_impl.cc
@@ -66,6 +66,7 @@
 #include "src/tint/transform/simplify_pointers.h"
 #include "src/tint/transform/unshadow.h"
 #include "src/tint/transform/unwind_discard_functions.h"
+#include "src/tint/transform/vectorize_scalar_matrix_constructors.h"
 #include "src/tint/transform/zero_init_workgroup_memory.h"
 #include "src/tint/utils/defer.h"
 #include "src/tint/utils/map.h"
@@ -198,6 +199,7 @@
     manager.Add<transform::ExpandCompoundAssignment>();
     manager.Add<transform::PromoteSideEffectsToDecl>();
     manager.Add<transform::UnwindDiscardFunctions>();
+    manager.Add<transform::VectorizeScalarMatrixConstructors>();
     manager.Add<transform::SimplifyPointers>();
     manager.Add<transform::RemovePhonies>();
     // ArrayLengthFromUniform must come after InlinePointerLets and Simplify, as
@@ -1080,6 +1082,55 @@
         return EmitZeroValue(out, type);
     }
 
+    if (auto* mat = call->Type()->As<sem::Matrix>()) {
+        if (ctor->Parameters().size() == 1) {
+            // Matrix constructor with single scalar.
+            auto fn = utils::GetOrCreate(matrix_scalar_ctors_, mat, [&]() -> std::string {
+                TextBuffer b;
+                TINT_DEFER(helpers_.Append(b));
+
+                auto name = UniqueIdentifier("build_mat" + std::to_string(mat->columns()) + "x" +
+                                             std::to_string(mat->rows()));
+                {
+                    auto l = line(&b);
+                    if (!EmitType(l, mat, ast::StorageClass::kNone, ast::Access::kUndefined, "")) {
+                        return "";
+                    }
+                    l << " " << name << "(";
+                    if (!EmitType(l, mat->type(), ast::StorageClass::kNone, ast::Access::kUndefined,
+                                  "")) {
+                        return "";
+                    }
+                    l << " value) {";
+                }
+                {
+                    ScopedIndent si(&b);
+                    auto l = line(&b);
+                    l << "return ";
+                    if (!EmitType(l, mat, ast::StorageClass::kNone, ast::Access::kUndefined, "")) {
+                        return "";
+                    }
+                    l << "(";
+                    for (uint32_t i = 0; i < mat->columns() * mat->rows(); i++) {
+                        l << ((i > 0) ? ", value" : "value");
+                    }
+                    l << ");";
+                }
+                line(&b) << "}";
+                return name;
+            });
+            if (fn.empty()) {
+                return false;
+            }
+            out << fn << "(";
+            if (!EmitExpression(out, call->Arguments()[0]->Declaration())) {
+                return false;
+            }
+            out << ")";
+            return true;
+        }
+    }
+
     bool brackets = type->IsAnyOf<sem::Array, sem::Struct>();
 
     // For single-value vector initializers, swizzle the scalar to the right