Martha Mercer, née Dana (1872–1960) was a US art collector and philanthropist.

She became friends with Isabella Stewart Gardner who arranged for her to have her portrait painted by Anders Zorn in 1899.

Together they designed and built Aldie Mansion in the Tudor revival style, today owned by the Heritage Conservancy of Bucks County.

[3] Dana Mercer gave her portrait by Zorn to the museum in 1928.

The museum also has another painting formerly in her collection, Man on Horseback by Gerard ter Borch.