diff --git a/runtime/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/Formatter.java b/runtime/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/Formatter.java
new file mode 100644
index 0000000..d6eeb0e
--- /dev/null
+++ b/runtime/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/Formatter.java
@@ -0,0 +1,106 @@
+package eu.mulk.quarkus.googlecloud.jsonlogging;
+
+import java.io.PrintWriter;
+import java.io.StringWriter;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.logging.Level;
+import org.jboss.logmanager.ExtFormatter;
+import org.jboss.logmanager.ExtLogRecord;
+
+/**
+ * Formats log records as JSON for consumption by Google Cloud Logging.
+ *
+ * <p>Meant to be used in containers running on Google Kubernetes Engine (GKE).
+ *
+ * @see LogEntry
+ */
+class Formatter extends ExtFormatter {
+
+  private static final String TRACE_LEVEL = "TRACE";
+  private static final String DEBUG_LEVEL = "DEBUG";
+  private static final String INFO_LEVEL = "INFO";
+  private static final String WARNING_LEVEL = "WARNING";
+  private static final String ERROR_LEVEL = "ERROR";
+
+  private static final String ERROR_EVENT_TYPE =
+      "type.googleapis.com/google.devtools.clouderrorreporting.v1beta1.ReportedErrorEvent";
+
+  @Override
+  public String format(ExtLogRecord logRecord) {
+    var message = formatMessageWithStackTrace(logRecord);
+
+    List<StructuredParameter> parameters = new ArrayList<>();
+    Map<String, String> labels = new HashMap<>();
+    if (logRecord.getParameters() != null) {
+      for (var parameter : logRecord.getParameters()) {
+        if (parameter instanceof StructuredParameter sparam) {
+          parameters.add(sparam);
+        } else if (parameter instanceof Label label) {
+          labels.put(label.key(), label.value());
+        }
+      }
+    }
+
+    var mdc = logRecord.getMdcCopy();
+    var ndc = logRecord.getNdc();
+
+    var sourceLocation =
+        new LogEntry.SourceLocation(
+            logRecord.getSourceFileName(),
+            String.valueOf(logRecord.getSourceLineNumber()),
+            String.format(
+                "%s.%s", logRecord.getSourceClassName(), logRecord.getSourceMethodName()));
+
+    var entry =
+        new LogEntry(
+            message,
+            severityOf(logRecord.getLevel()),
+            new LogEntry.Timestamp(logRecord.getInstant()),
+            null,
+            null,
+            sourceLocation,
+            labels,
+            parameters,
+            mdc,
+            ndc,
+            logRecord.getLevel().intValue() >= 1000 ? ERROR_EVENT_TYPE : null);
+
+    return entry.json().build().toString() + "\n";
+  }
+
+  /**
+   * Formats the log message corresponding to {@code logRecord} including a stack trace of the
+   * {@link ExtLogRecord#getThrown()} exception if any.
+   */
+  private String formatMessageWithStackTrace(ExtLogRecord logRecord) {
+    var messageStringWriter = new StringWriter();
+    var messagePrintWriter = new PrintWriter(messageStringWriter);
+    messagePrintWriter.append(this.formatMessage(logRecord));
+
+    if (logRecord.getThrown() != null) {
+      messagePrintWriter.println();
+      logRecord.getThrown().printStackTrace(messagePrintWriter);
+    }
+
+    messagePrintWriter.close();
+    return messageStringWriter.toString();
+  }
+
+  /** Computes the Google Cloud Logging severity corresponding to a given {@link Level}. */
+  private static String severityOf(Level level) {
+    if (level.intValue() < 500) {
+      return TRACE_LEVEL;
+    } else if (level.intValue() < 700) {
+      return DEBUG_LEVEL;
+    } else if (level.intValue() < 900) {
+      return INFO_LEVEL;
+    } else if (level.intValue() < 1000) {
+      return WARNING_LEVEL;
+    } else {
+      return ERROR_LEVEL;
+    }
+  }
+}
diff --git a/runtime/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/GoogleCloudJsonLoggingRecorder.java b/runtime/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/GoogleCloudJsonLoggingRecorder.java
new file mode 100644
index 0000000..db2c2e9
--- /dev/null
+++ b/runtime/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/GoogleCloudJsonLoggingRecorder.java
@@ -0,0 +1,12 @@
+package eu.mulk.quarkus.googlecloud.jsonlogging;
+
+import io.quarkus.runtime.RuntimeValue;
+import io.quarkus.runtime.annotations.Recorder;
+import java.util.Optional;
+
+@Recorder
+public class GoogleCloudJsonLoggingRecorder {
+  public RuntimeValue<Optional<java.util.logging.Formatter>> initialize() {
+    return new RuntimeValue<>(Optional.of(new Formatter()));
+  }
+}
diff --git a/runtime/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/KeyValueParameter.java b/runtime/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/KeyValueParameter.java
new file mode 100644
index 0000000..5f582c9
--- /dev/null
+++ b/runtime/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/KeyValueParameter.java
@@ -0,0 +1,43 @@
+package eu.mulk.quarkus.googlecloud.jsonlogging;
+
+import java.math.BigDecimal;
+import java.math.BigInteger;
+import javax.json.Json;
+import javax.json.JsonObjectBuilder;
+import javax.json.JsonValue;
+
+public record KeyValueParameter(String key, JsonValue value) implements StructuredParameter {
+
+  public static KeyValueParameter of(String key, String value) {
+    return new KeyValueParameter(key, Json.createValue(value));
+  }
+
+  public static KeyValueParameter of(String key, int value) {
+    return new KeyValueParameter(key, Json.createValue(value));
+  }
+
+  public static KeyValueParameter of(String key, long value) {
+    return new KeyValueParameter(key, Json.createValue(value));
+  }
+
+  public static KeyValueParameter of(String key, double value) {
+    return new KeyValueParameter(key, Json.createValue(value));
+  }
+
+  public static KeyValueParameter of(String key, BigDecimal value) {
+    return new KeyValueParameter(key, Json.createValue(value));
+  }
+
+  public static KeyValueParameter of(String key, BigInteger value) {
+    return new KeyValueParameter(key, Json.createValue(value));
+  }
+
+  public static KeyValueParameter of(String key, boolean value) {
+    return new KeyValueParameter(key, value ? JsonValue.TRUE : JsonValue.FALSE);
+  }
+
+  @Override
+  public JsonObjectBuilder json() {
+    return Json.createObjectBuilder().add(key, value);
+  }
+}
diff --git a/runtime/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/Label.java b/runtime/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/Label.java
new file mode 100644
index 0000000..02f7034
--- /dev/null
+++ b/runtime/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/Label.java
@@ -0,0 +1,8 @@
+package eu.mulk.quarkus.googlecloud.jsonlogging;
+
+public record Label(String key, String value) {
+
+  public static Label of(String key, String value) {
+    return new Label(key, value);
+  }
+}
diff --git a/runtime/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/LogEntry.java b/runtime/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/LogEntry.java
new file mode 100644
index 0000000..4394033
--- /dev/null
+++ b/runtime/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/LogEntry.java
@@ -0,0 +1,103 @@
+package eu.mulk.quarkus.googlecloud.jsonlogging;
+
+import io.smallrye.common.constraint.Nullable;
+import java.time.Instant;
+import java.util.List;
+import java.util.Map;
+import javax.json.Json;
+import javax.json.JsonObject;
+import javax.json.JsonObjectBuilder;
+
+/**
+ * A JSON log entry compatible with Google Cloud Logging.
+ *
+ * <p>Roughly (but not quite) corresponds to Google Cloud Logging's <a
+ * href="https://cloud.google.com/logging/docs/reference/v2/rest/v2/LogEntry">LogEntry</a>
+ * structure.
+ *
+ * <p>A few of the fields are treated specially by the fluentd instance running in Google Kubernetes
+ * Engine. All other fields end up in the jsonPayload field on the Google Cloud Logging side.
+ */
+record LogEntry(
+    String message,
+    String severity,
+    Timestamp timestamp,
+    @Nullable String trace,
+    @Nullable String spanId,
+    SourceLocation sourceLocation,
+    Map<String, String> labels,
+    List<StructuredParameter> parameters,
+    Map<String, String> mappedDiagnosticContext,
+    @Nullable String nestedDiagnosticContext,
+    @Nullable String type) {
+
+  static record SourceLocation(
+      @Nullable String file, @Nullable String line, @Nullable String function) {
+
+    JsonObject json() {
+      return Json.createObjectBuilder()
+          .add("file", file)
+          .add("line", line)
+          .add("function", function)
+          .build();
+    }
+  }
+
+  static record Timestamp(long seconds, int nanos) {
+
+    Timestamp(Instant t) {
+      this(t.getEpochSecond(), t.getNano());
+    }
+
+    JsonObject json() {
+      return Json.createObjectBuilder().add("seconds", seconds).add("nanos", nanos).build();
+    }
+  }
+
+  JsonObjectBuilder json() {
+    var b = Json.createObjectBuilder();
+
+    if (trace != null) {
+      b.add("trace", trace);
+    }
+
+    if (spanId != null) {
+      b.add("spanId", spanId);
+    }
+
+    if (nestedDiagnosticContext != null && !nestedDiagnosticContext.isEmpty()) {
+      b.add("nestedDiagnosticContext", nestedDiagnosticContext);
+    }
+
+    if (!labels.isEmpty()) {
+      b.add("labels", jsonOfStringMap(labels));
+    }
+
+    if (type != null) {
+      b.add("@type", type);
+    }
+
+    return b.add("message", message)
+        .add("severity", severity)
+        .add("timestamp", timestamp.json())
+        .add("sourceLocation", sourceLocation.json())
+        .addAll(jsonOfStringMap(mappedDiagnosticContext))
+        .addAll(jsonOfParameterMap(parameters));
+  }
+
+  private static JsonObjectBuilder jsonOfStringMap(Map<String, String> stringMap) {
+    return stringMap.entrySet().stream()
+        .reduce(
+            Json.createObjectBuilder(),
+            (acc, x) -> acc.add(x.getKey(), x.getValue()),
+            JsonObjectBuilder::addAll);
+  }
+
+  private static JsonObjectBuilder jsonOfParameterMap(List<StructuredParameter> parameters) {
+    return parameters.stream()
+        .reduce(
+            Json.createObjectBuilder(),
+            (acc, p) -> acc.addAll(p.json()),
+            JsonObjectBuilder::addAll);
+  }
+}
diff --git a/runtime/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/StructuredParameter.java b/runtime/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/StructuredParameter.java
new file mode 100644
index 0000000..0b4a36e
--- /dev/null
+++ b/runtime/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/StructuredParameter.java
@@ -0,0 +1,7 @@
+package eu.mulk.quarkus.googlecloud.jsonlogging;
+
+import javax.json.JsonObjectBuilder;
+
+public interface StructuredParameter {
+  JsonObjectBuilder json();
+}