diff --git a/config/config.go b/config/config.go
index a4f9f77..cebf10d 100644
--- a/config/config.go
+++ b/config/config.go
@@ -3,6 +3,7 @@
 import (
 	"fmt"
 	"os"
+	"strconv"
 
 	"github.com/KorAP/Koral-Mapper/ast"
 	"github.com/KorAP/Koral-Mapper/parser"
@@ -196,6 +197,9 @@
 		Lists:      allLists,
 	}
 
+	// Apply environment variable overrides (ENV > config file)
+	ApplyEnvOverrides(result)
+
 	// Apply defaults if not specified
 	ApplyDefaults(result)
 
@@ -224,6 +228,32 @@
 	}
 }
 
+// ApplyEnvOverrides overrides configuration fields from environment variables.
+// All environment variables are uppercase and prefixed with KORAL_MAPPER_.
+// Non-empty environment values override any previously loaded config values.
+func ApplyEnvOverrides(config *MappingConfig) {
+	envMappings := map[string]*string{
+		"KORAL_MAPPER_SERVER":      &config.Server,
+		"KORAL_MAPPER_SDK":         &config.SDK,
+		"KORAL_MAPPER_STYLESHEET":  &config.Stylesheet,
+		"KORAL_MAPPER_SERVICE_URL": &config.ServiceURL,
+		"KORAL_MAPPER_COOKIE_NAME": &config.CookieName,
+		"KORAL_MAPPER_LOG_LEVEL":   &config.LogLevel,
+	}
+
+	for envKey, field := range envMappings {
+		if val := os.Getenv(envKey); val != "" {
+			*field = val
+		}
+	}
+
+	if val := os.Getenv("KORAL_MAPPER_PORT"); val != "" {
+		if port, err := strconv.Atoi(val); err == nil {
+			config.Port = port
+		}
+	}
+}
+
 // validateMappingLists validates a slice of mapping lists (without duplicate ID checking)
 func validateMappingLists(lists []MappingList) error {
 	for i, list := range lists {