Which African lake is the source of the Blue Nile?

Lake Tana is the source of the Blue Nile.

Lake Tana lies in northwestern Ethiopia at an elevation of about 1,786 metres. The Blue Nile leaves the lake near Bahir Dar and then travels through Ethiopia before entering Sudan, where it eventually joins the White Nile at Khartoum.

Tana is Ethiopia's largest lake and covers roughly 3,000 to 3,500 square kilometres, depending on seasonal water levels. Several rivers feed it, while the Abay River is the local Ethiopian name for the Blue Nile. The famous Blue Nile Falls are downstream of the lake.

The lake contains numerous islands and peninsulas, many of which host historic Ethiopian Orthodox monasteries and churches. Lake Tana is sometimes mistakenly called the source of the entire Nile. More precisely, it is the source of the Blue Nile, while the White Nile's farthest headwaters are associated with the Great Lakes region of East Africa.