Leioa (Spanish: Lejona) is a municipality in Biscay, Basque Country, in northern Spain. It is located south of Getxo and Berango delimitating east and south with Erandio, Portugalete and Sestao. Today it is part of the Bilbao conurbation. Its population in 2019 was 31,795. Leioa has an area of 8.36 square kilometres (3.23 sq mi). The Udondo river constitutes the eastern limit of the municipality.

Leioa has its origins in 1526, before which it was part of the "anteiglesia de Erandio". It was a village with no more than 8000 people until the 1960s, when development came its way, as Bilbao expanded. Its population experienced a rapid increase in the 1970s, and a more moderate growth afterwards. It has become a part of metropolitan Bilbao.

The municipality of Leioa still retains much of its agricultural past and out of the urban centre many traditional Basque houses can still be seen on little family farms, though rapid development puts their long-term future in question. The University of the Basque Country (EHU-UPV Euskal Herriko Unibertsitatea - Universidad del Pais Vasco) has most faculties within this municipality.

Two consecutive stations of Line 1 of the Metro Bilbao rapid transit system are located in Leioa: Leioa and Lamiako.