Beira Lake (/ˈbeɪrə/; Sinhala: බේරේ වැව, romanized: Bērē væva (IPA: [beːreː ˈʋæʋə]); Tamil: பேரே ஏரி, romanized: Pērē ēri (IPA: [peːɾeː eːɾi])) is a man-made lake in the centre of the city of Colombo in Sri Lanka.

The lake was built by the Portuguese to provide protection to Colombo from enemies, mainly local kings.

After informing the officials at the fort about this stream, it was connected to the moat they had dug, creating Beira Lake.

Then the lake was completely connected with the sea from both sides, separating the Colombo Fort from the mainland.

Sithawaka Rajasinghe) succeeded in 1587 in draining the crocodile infested lake by cutting off several canals but failed to defeat the Portuguese as they brought reinforcements from India through sea.

After the British took control they removed the crocodiles and developed the area surrounding the lake for recreational activities such as rowing and yachting.

The area around the lake was popular for parties including a grand ball that was held to celebrate the news of British victory in Waterloo.

With maximum length of 1.6 km (1 mi) the lake has been home to Colombo Rowing Club for over 140 years.

Joseph's college Colombo, the only school in Sri Lanka to have its very own Rowing pier is situated on the banks of the Beira lake.

The lake with many government owned properties has been earmarked for development including a casino district on its McCullum road water front.

The lake gets its famous green colour and unusually bad odour due to the result of pollution over hundreds of years and algae that is present in the water.

The bad smell is mostly prominent during dry weather, due to the high rates of evaporation and it fades off with the arrival of the rainy season.

But contrary to the canal system of Colombo, the lake contains water with a very alkaline pH value got by primary production and continuous bloom.

Under the project the Beira lake is expected to be cleaned and developed with Singaporean assistance and private sector involvement.