diff --git a/modules/caddytls/connpolicy.go b/modules/caddytls/connpolicy.go
index c38ad0d4b..852c78d54 100644
--- a/modules/caddytls/connpolicy.go
+++ b/modules/caddytls/connpolicy.go
@@ -107,7 +107,8 @@ func (cp ConnectionPolicies) TLSConfig(ctx caddy.Context) *tls.Config {
 				if sni, ok := m.(MatchServerName); ok {
 					for _, sniName := range sni {
 						// index for fast lookups during handshakes
-						indexedBySNI[sniName] = append(indexedBySNI[sniName], p)
+						indexName := asciiServerNameForMatch(sniName)
+						indexedBySNI[indexName] = append(indexedBySNI[indexName], p)
 					}
 				}
 			}
@@ -118,7 +119,7 @@ func (cp ConnectionPolicies) TLSConfig(ctx caddy.Context) *tls.Config {
 		// filter policies by SNI first, if possible, to speed things up
 		// when there may be lots of policies
 		possiblePolicies := cp
-		if indexedPolicies, ok := indexedBySNI[hello.ServerName]; ok {
+		if indexedPolicies, ok := indexedBySNI[asciiServerNameForMatch(hello.ServerName)]; ok {
 			possiblePolicies = indexedPolicies
 		}
 
diff --git a/modules/caddytls/connpolicy_test.go b/modules/caddytls/connpolicy_test.go
index 82ecbc40d..b3c091d47 100644
--- a/modules/caddytls/connpolicy_test.go
+++ b/modules/caddytls/connpolicy_test.go
@@ -15,6 +15,8 @@
 package caddytls
 
 import (
+	"context"
+	"crypto/tls"
 	"encoding/json"
 	"fmt"
 	"reflect"
@@ -24,6 +26,40 @@ import (
 	"github.com/caddyserver/caddy/v2/caddyconfig/caddyfile"
 )
 
+func TestConnectionPolicyIDNSNIMatcherFastPath(t *testing.T) {
+	ctx, cancel := caddy.NewContext(caddy.Context{Context: context.Background()})
+	defer cancel()
+
+	targetTLSConfig := &tls.Config{ClientAuth: tls.RequireAnyClientCert}
+	policies := ConnectionPolicies{
+		{
+			matchers:  []ConnectionMatcher{MatchServerName{"つ.Localhost"}},
+			TLSConfig: targetTLSConfig,
+		},
+	}
+
+	const sniFastPathThreshold = 30
+	for i := len(policies); i < sniFastPathThreshold; i++ {
+		policies = append(policies, &ConnectionPolicy{
+			matchers:  []ConnectionMatcher{MatchServerName{fmt.Sprintf("example-%d.localhost", i)}},
+			TLSConfig: &tls.Config{},
+		})
+	}
+	policies = append(policies, &ConnectionPolicy{
+		matchers:  []ConnectionMatcher{MatchServerName{"xn--k9j.localhost"}},
+		TLSConfig: &tls.Config{ClientAuth: tls.NoClientCert},
+	})
+
+	tlsConfig := policies.TLSConfig(ctx)
+	got, err := tlsConfig.GetConfigForClient(&tls.ClientHelloInfo{ServerName: "XN--K9J.LOCALHOST"})
+	if err != nil {
+		t.Fatalf("GetConfigForClient() error = %v", err)
+	}
+	if got != targetTLSConfig {
+		t.Fatalf("expected Unicode IDN policy to match before later punycode policy")
+	}
+}
+
 func TestClientAuthenticationUnmarshalCaddyfileWithDirectiveName(t *testing.T) {
 	const test_der_1 = `MIIDSzCCAjOgAwIBAgIUfIRObjWNUA4jxQ/0x8BOCvE2Vw4wDQYJKoZIhvcNAQELBQAwFjEUMBIGA1UEAwwLRWFzeS1SU0EgQ0EwHhcNMTkwODI4MTYyNTU5WhcNMjkwODI1MTYyNTU5WjAWMRQwEgYDVQQDDAtFYXN5LVJTQSBDQTCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBAK5m5elxhQfMp/3aVJ4JnpN9PUSz6LlP6LePAPFU7gqohVVFVtDkChJAG3FNkNQNlieVTja/bgH9IcC6oKbROwdY1h0MvNV8AHHigvl03WuJD8g2ReVFXXwsnrPmKXCFzQyMI6TYk3m2gYrXsZOU1GLnfMRC3KAMRgE2F45twOs9hqG169YJ6mM2eQjzjCHWI6S2/iUYvYxRkCOlYUbLsMD/AhgAf1plzg6LPqNxtdlwxZnA0ytgkmhK67HtzJu0+ovUCsMv0RwcMhsEo9T8nyFAGt9XLZ63X5WpBCTUApaAUhnG0XnerjmUWb6eUWw4zev54sEfY5F3x002iQaW6cECAwEAAaOBkDCBjTAdBgNVHQ4EFgQU4CBUbZsS2GaNIkGRz/cBsD5ivjswUQYDVR0jBEowSIAU4CBUbZsS2GaNIkGRz/cBsD5ivjuhGqQYMBYxFDASBgNVBAMMC0Vhc3ktUlNBIENBghR8hE5uNY1QDiPFD/THwE4K8TZXDjAMBgNVHRMEBTADAQH/MAsGA1UdDwQEAwIBBjANBgkqhkiG9w0BAQsFAAOCAQEAKB3V4HIzoiO/Ch6WMj9bLJ2FGbpkMrcb/Eq01hT5zcfKD66lVS1MlK+cRL446Z2b2KDP1oFyVs+qmrmtdwrWgD+nfe2sBmmIHo9m9KygMkEOfG3MghGTEcS+0cTKEcoHYWYyOqQh6jnedXY8Cdm4GM1hAc9MiL3/sqV8YCVSLNnkoNysmr06/rZ0MCUZPGUtRmfd0heWhrfzAKw2HLgX+RAmpOE2MZqWcjvqKGyaRiaZks4nJkP6521aC2Lgp0HhCz1j8/uQ5ldoDszCnu/iro0NAsNtudTMD+YoLQxLqdleIh6CW+illc2VdXwj7mn6J04yns9jfE2jRjW/yTLFuQ==`
 	const test_cert_file_1 = "../../caddytest/caddy.ca.cer"
diff --git a/modules/caddytls/matchers.go b/modules/caddytls/matchers.go
index dfbec94cc..597450ef7 100644
--- a/modules/caddytls/matchers.go
+++ b/modules/caddytls/matchers.go
@@ -28,6 +28,7 @@ import (
 	"github.com/caddyserver/certmagic"
 	"go.uber.org/zap"
 	"go.uber.org/zap/zapcore"
+	"golang.org/x/net/idna"
 
 	"github.com/caddyserver/caddy/v2"
 	"github.com/caddyserver/caddy/v2/caddyconfig/caddyfile"
@@ -69,15 +70,45 @@ func (m MatchServerName) Match(hello *tls.ClientHelloInfo) bool {
 		repl = caddy.NewReplacer()
 	}
 
+	serverName := asciiServerNameForMatch(hello.ServerName)
 	for _, name := range m {
-		rs := repl.ReplaceAll(name, "")
-		if certmagic.MatchWildcard(hello.ServerName, rs) {
+		rs := asciiServerNameForMatch(repl.ReplaceAll(name, ""))
+		if certmagic.MatchWildcard(serverName, rs) {
 			return true
 		}
 	}
 	return false
 }
 
+func asciiServerNameForMatch(name string) string {
+	if name == "" {
+		return name
+	}
+
+	// SNI is ASCII on the wire, but config can use Unicode IDNs.
+	ascii, err := idna.ToASCII(name)
+	if err == nil {
+		return strings.ToLower(ascii)
+	}
+
+	if !strings.Contains(name, "*") {
+		return strings.ToLower(name)
+	}
+
+	labels := strings.Split(name, ".")
+	for i, label := range labels {
+		if label == "" || label == "*" {
+			continue
+		}
+		ascii, err := idna.ToASCII(label)
+		if err != nil {
+			return strings.ToLower(name)
+		}
+		labels[i] = strings.ToLower(ascii)
+	}
+	return strings.Join(labels, ".")
+}
+
 // UnmarshalCaddyfile sets up the MatchServerName from Caddyfile tokens. Syntax:
 //
 //	sni <domains...>
diff --git a/modules/caddytls/matchers_test.go b/modules/caddytls/matchers_test.go
index 824f72070..8b597b188 100644
--- a/modules/caddytls/matchers_test.go
+++ b/modules/caddytls/matchers_test.go
@@ -79,6 +79,26 @@ func TestServerNameMatcher(t *testing.T) {
 			input:  "sub2.sub.example.com",
 			expect: true,
 		},
+		{
+			names:  []string{"つ.localhost"},
+			input:  "xn--k9j.localhost",
+			expect: true,
+		},
+		{
+			names:  []string{"つ.Localhost"},
+			input:  "XN--K9J.LOCALHOST",
+			expect: true,
+		},
+		{
+			names:  []string{"*.つ.localhost"},
+			input:  "sub.xn--k9j.localhost",
+			expect: true,
+		},
+		{
+			names:  []string{"*.つ.Localhost"},
+			input:  "Sub.XN--K9J.LOCALHOST",
+			expect: true,
+		},
 	} {
 		chi := &tls.ClientHelloInfo{ServerName: tc.input}
 		actual := MatchServerName(tc.names).Match(chi)