Which Ptolemaic ruler completed the Lighthouse of Alexandria?

Ptolemy II Philadelphus completed the Lighthouse of Alexandria.

Construction began during the reign of Ptolemy I Soter, who founded the Ptolemaic dynasty after the death of Alexander the Great. The lighthouse was completed under his son, Ptolemy II Philadelphus, in the early third century BC. It stood on the island of Pharos beside Alexandria and gave its name to the general term “pharos” for a lighthouse in several languages.

The building helped guide ships into Alexandria’s busy harbor and also served as a monumental display of Ptolemaic power. Ancient descriptions portray it as a tall, multi-level tower topped by a light and reflective apparatus, though details of its exact design are uncertain.

The lighthouse survived for many centuries but was progressively damaged by earthquakes. Its stones were later reused in the foundations of the Qaitbay Citadel, which occupies the site today.