North Bull Island is a national nature reserve in Dublin Bay on the Northside of Dublin. It is technically man-made, as it is a direct result of the North Bull Wall being constructed over 200 years ago.

During the 17th to the 18th centuries, Dublin City gradually became more prosperous leading Dublin Port to become much busier as the main point for goods to be brought into the country. However, the bay was prone to silting with sandbanks developing at the mouth of the river and proved extremely hazardous for ships coming in and out. After a couple of disastrous shipwrecks, the North Bull Wall was built in the 1800s,

As a result of the wall, the sandbanks which ships once ran aground on, grew larger and developed into an island above the water. Over the last 2 Centuries, it has naturally developed into a haven for local and visiting wildlife.

Installed in 1972, a significant addition was added to the wall, a statue of Réalt na Mara ('Our Lady, Star of the Sea'). The statue depicts Our Lady with a halo of 12 stars made of Waterford glass. Perched atop a globe, she watches over Dublin port workers and seafarers alike. The monument is floodlit at night and visible across Dublin Bay.

The island contains a wide range of natural habitats which include intertidal mudflats, salt marsh, freshwater marsh, dunes, and beach area. These individual habitats are vital to an extraordinary wealth of wildlife which live, breed, and eat on Bull Island. The area has several nature conservation designations for the habitats and species it supports. It is designated as a special amenity area for both its aesthetic and recreational value and is an integral part of the Dublin Bay Biosphere. 

The island is home at various times of the year to 8,000 wildfowl and 26,000 waders, 180 different bird species, and 300 species of plants. There are six mammal species on the island including Irish Hares, European Rabbits, Brown Rats, Red Foxes, Hedgehogs, and Field Mice.