The Lehoullier Building is a historic mill tenement house at 161-169 Main Street in Somersworth, New Hampshire.

Built in 1843, it is one of two surviving tenement houses of the many that once lined Main Street near the Great Falls Manufacturing Company.

The ground floor of each section has a center entrance flanked by paired sash windows.

[2] The tenement was built by Thomas Parks and Job Harris c. 1843 under a grant from the Great Falls Manufacturing Company, which operated the major textile mills in Somersworth.

The ground-floor spaces were adapted for commercial use, and the upper-floor exteriors were rearranged to provide access to the upper units from the back of the building.