North Bull Lighthouse, Lighthouse at the mouth of the River Liffey, County Dublin, Ireland

North Bull Lighthouse is a green metal tower standing at the entrance of Dublin Port, rising roughly 15 meters high. It produces a green flash every four seconds and can be seen from up to 10 nautical miles away by ships entering the bay.

The lighthouse was built in 1880 by engineer Bindon Blood Stoney to handle the growing ship traffic at Dublin Port. It was a key addition to make navigation safer in an expanding harbor.

The green light follows the convention of green on the right (starboard) and red on the left (port) when entering the dredged channel. The 1923 British Pilot shows this was not always so: North Bull then had a red tower, and Poolbeg was painted black.

The lighthouse is visible from the shoreline and accessible from various viewing points around Dublin's waterfront. For the best view of the structure, visiting from the harbor side or nearby coastal areas works well.

The tower's four-storey profile changed over time: an early photograph shows a small lantern room at the top, later removed, with the light now shown from a pole in the same spot. Until 1923 a fog bell of 17 long cwt (860 kg) struck four times every thirty seconds; it is now disused.