The Baikal seal, Lake Baikal seal is a species of earless seal endemic to Lake Baikal in Siberia, Russia. Like the Caspian seal, it is related to the Arctic ringed seal. The Baikal seal is one of the smallest true seals and the only exclusively freshwater pinniped species.

The Baikal seal lives only in the waters of Lake Baikal. It is something of a mystery how Baikal seals came to live there in the first place. The skull structure of the Baikal seal suggests it is closely related to the Caspian seal. In addition, the morphological structures in both species suggest they are descended from Arctic ringed seals. They may have swum up rivers and streams or possibly Lake Baikal was linked to the ocean at some point through a large body of water, such as the Tethys Ocean, West Siberian Glacial Lake or West Siberian Plain, formed in a previous ice age. The seals are estimated to have inhabited Lake Baikal for some two million years.