Asa Belknap Foster (April 21, 1817 – November 1, 1877) was a Quebec businessman and political figure.

He represented Bedford division in the Senate of Canada from 1867 to 1876 as a Conservative member.

He was born in Newfane, Vermont in 1817, the son of Sewell Foster, and settled near Waterloo in Lower Canada with his parents in 1822.

He served as lieutenant in the local militia and was elected mayor for Waterloo in 1867.

The Conservatives believed that Foster had provided information to the Liberals that led to the Pacific Scandal; this belief was encouraged when Foster was given contracts to construct railways by the Liberals in 1874 and 1875.