diff --git a/CHANGELOG.md b/CHANGELOG.md
index c1e24aea..7ddc15ff 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,9 +1,12 @@
 CHANGELOG
 =========
 
-4.0.0
+4.0.0 (2025-11-10)
 ------------------
 
+**This is a major release with several breaking changes. Please see
+[UPGRADING.md](UPGRADING.md) for detailed migration instructions.**
+
 * Java 17 or greater is now required.
 * Added support for MaxMind DB files larger than 2GB. The library now uses
   an internal Buffer abstraction that can handle databases exceeding the
diff --git a/README.md b/README.md
index 6367d115..7197ef5c 100644
--- a/README.md
+++ b/README.md
@@ -16,7 +16,7 @@ To do this, add the dependency to your pom.xml:
     <dependency>
         <groupId>com.maxmind.db</groupId>
         <artifactId>maxmind-db</artifactId>
-        <version>3.2.0</version>
+        <version>4.0.0</version>
     </dependency>
 ```
 
@@ -29,7 +29,7 @@ repositories {
     mavenCentral()
 }
 dependencies {
-    compile 'com.maxmind.db:maxmind-db:3.2.0'
+    compile 'com.maxmind.db:maxmind-db:4.0.0'
 }
 ```
 
@@ -83,8 +83,8 @@ public class Lookup {
             DatabaseRecord<LookupResult> record
                 = reader.getRecord(address, LookupResult.class);
 
-            System.out.println(record.getData().getCountry().getIsoCode());
-            System.out.println(record.getNetwork());
+            System.out.println(record.data().getCountry().getIsoCode());
+            System.out.println(record.network());
         }
     }
 
@@ -214,7 +214,7 @@ while(networks.hasNext()) {
     DatabaseRecord<Map<String, String>> iteration = networks.next();
 
     // Get the data.
-    Map<String, String> data = iteration.getData();
+    Map<String, String> data = iteration.data();
 
     // The IP Address
     InetAddress ipAddress = InetAddress.getByName(data.get("ip"));
diff --git a/UPGRADING.md b/UPGRADING.md
new file mode 100644
index 00000000..090205b1
--- /dev/null
+++ b/UPGRADING.md
@@ -0,0 +1,255 @@
+# Upgrading to 4.0.0
+
+This guide covers the breaking changes introduced in version 4.0.0 and how to
+update your code.
+
+## Java Version Requirement
+
+**Java 17 or greater is now required.** If you are using Java 11, you must
+upgrade to Java 17 or later before upgrading to 4.0.0.
+
+## Record Conversion and Method Changes
+
+The `DatabaseRecord`, `Metadata`, and `Network` classes have been converted to
+Java records. This means getter methods have been replaced with record accessor
+methods.
+
+### DatabaseRecord Changes
+
+**Before (3.x):**
+
+```java
+DatabaseRecord<MyData> record = reader.getRecord(address, MyData.class);
+MyData data = record.getData();
+Network network = record.getNetwork();
+```
+
+**After (4.0.0):**
+
+```java
+DatabaseRecord<MyData> record = reader.getRecord(address, MyData.class);
+MyData data = record.data();
+Network network = record.network();
+```
+
+**Find and replace:**
+
+- `record.getData()` → `record.data()`
+- `record.getNetwork()` → `record.network()`
+
+### Network Changes
+
+**Before (3.x):**
+
+```java
+InetAddress address = network.getNetworkAddress();
+int prefixLength = network.getPrefixLength();
+```
+
+**After (4.0.0):**
+
+```java
+InetAddress address = network.networkAddress();
+int prefixLength = network.prefixLength();
+```
+
+**Find and replace:**
+
+- `network.getNetworkAddress()` → `network.networkAddress()`
+- `network.getPrefixLength()` → `network.prefixLength()`
+
+### Metadata Changes
+
+All getter methods on `Metadata` have been replaced with record accessor
+methods. Remove the `get` prefix and use camelCase instead.
+
+**Before (3.x):**
+
+```java
+Metadata metadata = reader.getMetadata();
+int majorVersion = metadata.getBinaryFormatMajorVersion();
+String dbType = metadata.getDatabaseType();
+List<String> languages = metadata.getLanguages();
+```
+
+**After (4.0.0):**
+
+```java
+Metadata metadata = reader.getMetadata();
+int majorVersion = metadata.binaryFormatMajorVersion();
+String dbType = metadata.databaseType();
+List<String> languages = metadata.languages();
+```
+
+**Common replacements:**
+
+- `getBinaryFormatMajorVersion()` → `binaryFormatMajorVersion()`
+- `getBinaryFormatMinorVersion()` → `binaryFormatMinorVersion()`
+- `getDatabaseType()` → `databaseType()`
+- `getLanguages()` → `languages()`
+- `getDescription()` → `description()`
+- `getIpVersion()` → `ipVersion()`
+- `getNodeCount()` → `nodeCount()`
+- `getRecordSize()` → `recordSize()`
+
+### Build Time Change (Date → Instant)
+
+The `getBuildDate()` method has been replaced with `buildTime()`, which returns
+`java.time.Instant` instead of `java.util.Date`.
+
+**Before (3.x):**
+
+```java
+import java.util.Date;
+
+Metadata metadata = reader.getMetadata();
+Date buildDate = metadata.getBuildDate();
+```
+
+**After (4.0.0):**
+
+```java
+import java.time.Instant;
+
+Metadata metadata = reader.getMetadata();
+Instant buildTime = metadata.buildTime();
+```
+
+If you need a `Date` object, you can convert:
+
+```java
+Date buildDate = Date.from(metadata.buildTime());
+```
+
+## DatabaseRecord Constructor Change
+
+If you are manually constructing `DatabaseRecord` instances, the legacy
+constructor has been removed.
+
+**Before (3.x):**
+
+```java
+DatabaseRecord<MyData> record = new DatabaseRecord<>(data, ipAddress, prefixLength);
+```
+
+**After (4.0.0):**
+
+```java
+Network network = new Network(ipAddress, prefixLength);
+DatabaseRecord<MyData> record = new DatabaseRecord<>(data, network);
+```
+
+## Deserialization Improvements
+
+### Automatic Constructor Selection
+
+If your classes use records or have a single public constructor, you may no
+longer need to annotate them with `@MaxMindDbConstructor`.
+
+**Before (3.x) - Required annotations:**
+
+```java
+public record Location(
+    @MaxMindDbParameter(name = "latitude") Double latitude,
+    @MaxMindDbParameter(name = "longitude") Double longitude
+) {}
+```
+
+**After (4.0.0) - Annotations optional when names match:**
+
+```java
+public record Location(
+    Double latitude,
+    Double longitude
+) {}
+```
+
+The canonical record constructor is used automatically, and component names
+match the database field names.
+
+### Parameter Name Support
+
+For non-record classes, if you compile with the `-parameters` flag, parameter
+names can be used instead of requiring `@MaxMindDbParameter` annotations.
+
+**Before (3.x):**
+
+```java
+@MaxMindDbConstructor
+public Location(
+    @MaxMindDbParameter(name = "latitude") Double latitude,
+    @MaxMindDbParameter(name = "longitude") Double longitude
+) {
+    this.latitude = latitude;
+    this.longitude = longitude;
+}
+```
+
+**After (4.0.0) - With `-parameters` flag:**
+
+```java
+@MaxMindDbConstructor
+public Location(Double latitude, Double longitude) {
+    this.latitude = latitude;
+    this.longitude = longitude;
+}
+```
+
+### New Injection Annotations
+
+4.0.0 introduces `@MaxMindDbIpAddress` and `@MaxMindDbNetwork` annotations for
+injecting lookup context into your constructors.
+
+**Example:**
+
+```java
+public record EnrichedData(
+    String city,
+    @MaxMindDbIpAddress InetAddress lookupIp,
+    @MaxMindDbNetwork Network network
+) {}
+```
+
+## Large Database Support (>2GB)
+
+Version 4.0.0 adds support for MaxMind DB files larger than 2GB. This change is
+transparent to most users:
+
+- Files under 2GB continue to use a single `ByteBuffer` for optimal performance
+- Files 2GB and larger automatically use a multi-buffer implementation
+- No code changes required in your application
+
+## Migration Checklist
+
+1. ✅ Upgrade to Java 17 or later
+2. ✅ Update Maven/Gradle dependency to 4.0.0
+3. ✅ Replace `record.getData()` with `record.data()`
+4. ✅ Replace `record.getNetwork()` with `record.network()`
+5. ✅ Replace `network.getNetworkAddress()` with `network.networkAddress()`
+6. ✅ Replace `network.getPrefixLength()` with `network.prefixLength()`
+7. ✅ Update all `Metadata` getter methods (remove `get` prefix, use camelCase)
+8. ✅ Replace `metadata.getBuildDate()` with `metadata.buildTime()` and change
+   type from `Date` to `Instant`
+9. ✅ Update any manual `DatabaseRecord` constructions to use `Network`
+   parameter
+10. ✅ (Optional) Remove unnecessary `@MaxMindDbParameter` annotations if using
+    records or `-parameters` flag
+
+## Finding Issues
+
+To help identify code that needs updating, you can search your codebase for:
+
+- `.getData()`
+- `.getNetwork()`
+- `.getNetworkAddress()`
+- `.getPrefixLength()`
+- `.getBuildDate()`
+- `.getBinaryFormatMajorVersion()` (and similar Metadata getters)
+- `new DatabaseRecord<>` (check for three-parameter constructor)
+
+## Support
+
+If you encounter issues during the upgrade, please check:
+
+- [GitHub Issues](https://github.com/maxmind/MaxMind-DB-Reader-java/issues)
+- [MaxMind Support](https://www.maxmind.com/en/support)
diff --git a/pom.xml b/pom.xml
index cab3d1a8..652f4f3d 100644
--- a/pom.xml
+++ b/pom.xml
@@ -3,7 +3,7 @@
     <modelVersion>4.0.0</modelVersion>
     <groupId>com.maxmind.db</groupId>
     <artifactId>maxmind-db</artifactId>
-    <version>4.0.0-SNAPSHOT</version>
+    <version>4.0.0</version>
     <packaging>jar</packaging>
     <name>MaxMind DB Reader</name>
     <description>Reader for MaxMind DB</description>
diff --git a/src/test/java/com/maxmind/db/ReaderTest.java b/src/test/java/com/maxmind/db/ReaderTest.java
index 20479831..890a95ac 100644
--- a/src/test/java/com/maxmind/db/ReaderTest.java
+++ b/src/test/java/com/maxmind/db/ReaderTest.java
@@ -2001,7 +2001,6 @@ private void testIpV4(Reader reader, File file) throws IOException {
         }
     }
 
-    // XXX - logic could be combined with above
     private void testIpV6(Reader reader, File file) throws IOException {
         var subnets = new String[] {"::1:ffff:ffff", "::2:0:0",
             "::2:0:40", "::2:0:50", "::2:0:58"};