Merrill Lake is a lake in the Moira River and Lake Ontario drainage basins that straddles the border between the Cashel portion of Tudor and Cashel, Hastings County and Addington Highlands, Lennox and Addington County in Ontario, Canada.

The northwest end of the lake lies in Tudor and Cashel, Hastings County, the rest in Addington Highlands, Lennox and Addington County.

The primary inflow is Merrill Creek from Todd Lakes at the north of the east bay, and there are six unnamed creek secondary inflows: one at the northwest, three at the north and two at the north of the east bay.

It flows via Partridge Creek, the Skootamatta River and the Moira River into the Bay of Quinte on Lake Ontario at Belleville.

This Eastern Ontario geographical article is a stub.