diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8621898..3785e72 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,12 @@
 CHANGELOG GEOIP-API
 ===================
 
+Unreleased
+----------
+
+* Respect optional `PORT` environment variable for the HTTP listen port
+  (defaults to `8080`), for platforms such as Dokku.
+
 2023-01 (2022-12-31)
 -------------------
 
diff --git a/Dockerfile b/Dockerfile
index 1727922..ba67309 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -47,6 +47,6 @@ COPY --from=builder "/build/GeoLite2-ASN.mmdb" /srv/GeoLite2-ASN.mmdb
 
 ENV CITY_DB_FILE /srv/GeoLite2-City.mmdb
 ENV ASN_DB_FILE  /srv/GeoLite2-ASN.mmdb
-HEALTHCHECK --interval=5s --timeout=1s CMD curl -f http://localhost:8080/actuator/health
+HEALTHCHECK --interval=5s --timeout=1s CMD curl -f http://localhost:${PORT:-8080}/actuator/health
 EXPOSE 8080
 CMD exec /srv/geoip-api
diff --git a/README.md b/README.md
index 18913a8..d3db324 100644
--- a/README.md
+++ b/README.md
@@ -51,6 +51,7 @@ variables:
 
 | Variable | Description | Default value |
 | -------- | ----------- | ------------- |
+| PORT | HTTP port the service listens on (used by platforms such as Dokku). | `8080` |
 | CITY_DB_FILE | The location of the GeoIP2 City or GeoLite2 database file. | `/srv/GeoLite2-City.mmdb` |
 | ASN_DB_FILE | The location of the GeoIP2 ASN database file. | `/srv/GeoLite2-ASN.mmdb` |
 | ISP_DB_FILE | The location of the GeoIP2 ISP database file. | (none) |
diff --git a/src/main/resources/application.yml b/src/main/resources/application.yml
index d2b5dc4..d631057 100644
--- a/src/main/resources/application.yml
+++ b/src/main/resources/application.yml
@@ -1,2 +1,5 @@
 spring.main.banner-mode: "off"
 management.endpoints.web.exposure.include: health, prometheus
+
+# Honor PORT when set by platforms such as Dokku/Heroku; default to 8080.
+server.port: ${PORT:8080}