diff --git a/CHANGELOG.md b/CHANGELOG.md
index cf67c1c..cfc656b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,9 @@
+## 1.25.5 (June 18, 2024)
+
+IMPROVEMENTS:
+
+* Add `RegexNotMatches` Plugin Framework validator
+
 ## 1.25.4 (June 4, 2024)
 
 IMPROVEMENTS:
diff --git a/validator/fw/string/regex_not_match.go b/validator/fw/string/regex_not_match.go
new file mode 100644
index 0000000..f2ebde5
--- /dev/null
+++ b/validator/fw/string/regex_not_match.go
@@ -0,0 +1,61 @@
+package string
+
+import (
+	"context"
+	"fmt"
+	"regexp"
+
+	"github.com/hashicorp/terraform-plugin-framework-validators/helpers/validatordiag"
+	"github.com/hashicorp/terraform-plugin-framework/schema/validator"
+)
+
+// Ensure our implementation satisfies the validator.String interface.
+var _ validator.String = &regexNotMatchesValidator{}
+
+type regexNotMatchesValidator struct {
+	regexp  *regexp.Regexp
+	message string
+}
+
+func (v regexNotMatchesValidator) Description(_ context.Context) string {
+	if v.message != "" {
+		return v.message
+	}
+	return fmt.Sprintf("value must not match regular expression '%s'", v.regexp)
+}
+
+func (v regexNotMatchesValidator) MarkdownDescription(ctx context.Context) string {
+	return v.Description(ctx)
+}
+
+func (v regexNotMatchesValidator) ValidateString(ctx context.Context, request validator.StringRequest, response *validator.StringResponse) {
+	if request.ConfigValue.IsNull() || request.ConfigValue.IsUnknown() {
+		return
+	}
+
+	value := request.ConfigValue.ValueString()
+
+	if v.regexp.MatchString(value) {
+		response.Diagnostics.Append(validatordiag.InvalidAttributeValueMatchDiagnostic(
+			request.Path,
+			v.Description(ctx),
+			value,
+		))
+	}
+}
+
+// RegexNotMatches returns an AttributeValidator which ensures that any configured
+// attribute value:
+//
+//   - Is a string.
+//   - Not matches the given regular expression https://github.com/google/re2/wiki/Syntax.
+//
+// Null (unconfigured) and unknown (known after apply) values are skipped.
+// Optionally an error message can be provided to return something friendlier
+// than "value must not match regular expression 'regexp'".
+func RegexNotMatches(regexp *regexp.Regexp, message string) validator.String {
+	return regexNotMatchesValidator{
+		regexp:  regexp,
+		message: message,
+	}
+}