diff --git a/modules/markup/renderer.go b/modules/markup/renderer.go
index 05dd512815..b1c3d35e73 100644
--- a/modules/markup/renderer.go
+++ b/modules/markup/renderer.go
@@ -198,10 +198,28 @@ func RegisterRenderer(renderer Renderer) {
 	}
 }
 
-// GetRendererByFileName get renderer by filename
-func GetRendererByFileName(filename string) Renderer {
-	extension := strings.ToLower(filepath.Ext(filename))
-	return extRenderers[extension]
+// FullExtension returns the full extension of path, i.e. everything after and including
+// the first period in the basename of path.
+func FullExtension(path string) string {
+	_, extension, found := strings.Cut(strings.ToLower(filepath.Base(path)), ".")
+	if !found {
+		return ""
+	}
+	return "." + extension
+}
+
+// GetRendererByExtension returns the most specific registered renderer for extension.
+func GetRendererByExtension(extension string) Renderer {
+	_, extension, found := strings.Cut(extension, ".")
+	checkedExtensions := 0
+	for found && checkedExtensions < 10 {
+		if renderer, ok := extRenderers["."+extension]; ok {
+			return renderer
+		}
+		checkedExtensions++
+		_, extension, found = strings.Cut(extension, ".")
+	}
+	return nil
 }
 
 // GetRendererByType returns a renderer according type
@@ -350,6 +368,20 @@ func renderByType(ctx *RenderContext, input io.Reader, output io.Writer) error {
 	return ErrUnsupportedRenderType{ctx.Type}
 }
 
+// ErrMissingExtension represents the error when a path does not have any extension.
+type ErrMissingExtension struct {
+	Path string
+}
+
+func IsErrMissingExtension(err error) bool {
+	_, ok := err.(ErrMissingExtension)
+	return ok
+}
+
+func (err ErrMissingExtension) Error() string {
+	return fmt.Sprintf("path '%s' does not have an extension", err.Path)
+}
+
 // ErrUnsupportedRenderExtension represents the error when extension doesn't supported to render
 type ErrUnsupportedRenderExtension struct {
 	Extension string
@@ -365,8 +397,11 @@ func (err ErrUnsupportedRenderExtension) Error() string {
 }
 
 func renderFile(ctx *RenderContext, input io.Reader, output io.Writer) error {
-	extension := strings.ToLower(filepath.Ext(ctx.RelativePath))
-	if renderer, ok := extRenderers[extension]; ok {
+	extension := FullExtension(ctx.RelativePath)
+	if extension == "" {
+		return ErrMissingExtension{ctx.RelativePath}
+	}
+	if renderer := GetRendererByExtension(extension); renderer != nil {
 		if r, ok := renderer.(ExternalRenderer); ok && r.DisplayInIFrame() {
 			if !ctx.InStandalonePage {
 				// for an external render, it could only output its content in a standalone page
@@ -381,7 +416,7 @@ func renderFile(ctx *RenderContext, input io.Reader, output io.Writer) error {
 
 // Type returns if markup format via the filename
 func Type(filename string) string {
-	if parser := GetRendererByFileName(filename); parser != nil {
+	if parser := GetRendererByExtension(FullExtension(filename)); parser != nil {
 		return parser.Name()
 	}
 	return ""
@@ -389,7 +424,7 @@ func Type(filename string) string {
 
 // IsMarkupFile reports whether file is a markup type file
 func IsMarkupFile(name, markup string) bool {
-	if parser := GetRendererByFileName(name); parser != nil {
+	if parser := GetRendererByExtension(FullExtension(name)); parser != nil {
 		return parser.Name() == markup
 	}
 	return false
diff --git a/routers/common/markup.go b/routers/common/markup.go
index 715d7d883f..f581d22ff7 100644
--- a/routers/common/markup.go
+++ b/routers/common/markup.go
@@ -94,7 +94,7 @@ func (re *Renderer) RenderMarkup(ctx *context.Base, repo *context.Repository) {
 		Type:         markupType,
 		RelativePath: relativePath,
 	}, strings.NewReader(re.Text), ctx.Resp); err != nil {
-		if markup.IsErrUnsupportedRenderExtension(err) {
+		if markup.IsErrUnsupportedRenderExtension(err) || markup.IsErrMissingExtension(err) {
 			ctx.Error(http.StatusUnprocessableEntity, err.Error())
 		} else {
 			ctx.Error(http.StatusInternalServerError, err.Error())
diff --git a/tests/integration/markup_external_test.go b/tests/integration/markup_external_test.go
index a7cbdf37cb..d95093a01b 100644
--- a/tests/integration/markup_external_test.go
+++ b/tests/integration/markup_external_test.go
@@ -7,10 +7,17 @@ import (
 	"bytes"
 	"io"
 	"net/http"
+	"net/url"
 	"strings"
 	"testing"
+	"time"
 
+	"forgejo.org/models/unit"
+	"forgejo.org/models/unittest"
+	user_model "forgejo.org/models/user"
+	"forgejo.org/modules/git"
 	"forgejo.org/modules/setting"
+	files_service "forgejo.org/services/repository/files"
 	"forgejo.org/tests"
 
 	"github.com/stretchr/testify/assert"
@@ -38,3 +45,72 @@ func TestExternalMarkupRenderer(t *testing.T) {
 	require.NoError(t, err)
 	assert.Equal(t, "<div>\n\ttest external renderer\n</div>", strings.TrimSpace(data))
 }
+
+func TestExternalMarkupRendererWithCompoundFileExtensions(t *testing.T) {
+	onApplicationRun(t, func(t *testing.T, u *url.URL) {
+		testCases := []struct {
+			path                      string
+			shouldUseExternalRenderer bool
+			expectedRenderedContent   string
+		}{
+			{"foo.abc.def.ghi.jkl.md", true, ".def.ghi.jkl.md renderer used"},
+			{"foo.def.ghi.jkl.md", true, ".def.ghi.jkl.md renderer used"},
+			{"foo.ghi.jkl.md", true, ".ghi.jkl.md renderer used"},
+			{"foo.jkl.md", false, "foo"},
+			{"foo.md", false, "foo"},
+		}
+
+		changeRepoFiles := []*files_service.ChangeRepoFile{}
+		for _, testCase := range testCases {
+			changeRepoFiles = append(changeRepoFiles,
+				&files_service.ChangeRepoFile{
+					Operation:     "create",
+					TreePath:      testCase.path,
+					ContentReader: strings.NewReader("foo"),
+				},
+			)
+		}
+
+		user := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 1})
+		repo, _, f := tests.CreateDeclarativeRepo(t, user, "", []unit.Type{unit.TypeCode}, nil, nil)
+		defer f()
+
+		_, err := files_service.ChangeRepoFiles(git.DefaultContext, repo, user, &files_service.ChangeRepoFilesOptions{
+			Files:   changeRepoFiles,
+			Message: "add files",
+			Author: &files_service.IdentityOptions{
+				Name:  user.Name,
+				Email: user.Email,
+			},
+			Committer: &files_service.IdentityOptions{
+				Name:  user.Name,
+				Email: user.Email,
+			},
+			Dates: &files_service.CommitDateOptions{
+				Author:    time.Now(),
+				Committer: time.Now(),
+			},
+		})
+		require.NoError(t, err)
+
+		for _, testCase := range testCases {
+			t.Run(testCase.path, func(t *testing.T) {
+				req := NewRequestf(t, "GET", "%s/src/branch/%s/%s", repo.HTMLURL(), repo.DefaultBranch, testCase.path)
+				resp := MakeRequest(t, req, http.StatusOK)
+				require.Equal(t, "text/html; charset=utf-8", resp.Header()["Content-Type"][0])
+
+				doc := NewHTMLParser(t, resp.Body)
+				var query string
+				if testCase.shouldUseExternalRenderer {
+					query = "div.file-view"
+				} else {
+					query = "div.file-view p"
+				}
+				p := doc.Find(query)
+				data, err := p.Html()
+				require.NoError(t, err)
+				assert.Equal(t, testCase.expectedRenderedContent, strings.TrimSpace(data))
+			})
+		}
+	})
+}
diff --git a/tests/mysql.ini.tmpl b/tests/mysql.ini.tmpl
index 4678cf5087..9a010daab1 100644
--- a/tests/mysql.ini.tmpl
+++ b/tests/mysql.ini.tmpl
@@ -140,3 +140,13 @@ NEED_POSTPROCESS = false
 [cache]
 # Disable caching so that data isn't kept in-memory between test cases
 ITEM_TTL = -1
+
+[markup.compound_file_extension]
+ENABLED = true
+FILE_EXTENSIONS = .ghi.jkl.md
+RENDER_COMMAND = echo .ghi.jkl.md renderer used
+
+[markup.compound_file_extension_2]
+ENABLED = true
+FILE_EXTENSIONS = .def.ghi.jkl.md
+RENDER_COMMAND = echo .def.ghi.jkl.md renderer used
diff --git a/tests/pgsql.ini.tmpl b/tests/pgsql.ini.tmpl
index 2e5dda5c59..ad56451bc3 100644
--- a/tests/pgsql.ini.tmpl
+++ b/tests/pgsql.ini.tmpl
@@ -154,3 +154,13 @@ NEED_POSTPROCESS = false
 [cache]
 # Disable caching so that data isn't kept in-memory between test cases
 ITEM_TTL = -1
+
+[markup.compound_file_extension]
+ENABLED = true
+FILE_EXTENSIONS = .ghi.jkl.md
+RENDER_COMMAND = echo .ghi.jkl.md renderer used
+
+[markup.compound_file_extension_2]
+ENABLED = true
+FILE_EXTENSIONS = .def.ghi.jkl.md
+RENDER_COMMAND = echo .def.ghi.jkl.md renderer used
diff --git a/tests/sqlite.ini.tmpl b/tests/sqlite.ini.tmpl
index 10280cae19..9511e6d2a5 100644
--- a/tests/sqlite.ini.tmpl
+++ b/tests/sqlite.ini.tmpl
@@ -141,3 +141,13 @@ NEED_POSTPROCESS = false
 [cache]
 # Disable caching so that data isn't kept in-memory between test cases
 ITEM_TTL = -1
+
+[markup.compound_file_extension]
+ENABLED = true
+FILE_EXTENSIONS = .ghi.jkl.md
+RENDER_COMMAND = echo .ghi.jkl.md renderer used
+
+[markup.compound_file_extension_2]
+ENABLED = true
+FILE_EXTENSIONS = .def.ghi.jkl.md
+RENDER_COMMAND = echo .def.ghi.jkl.md renderer used