Topsham (US: /ˈtɒp.sʌm/ ⓘTOP-sum) is a town in Sagadahoc County, Maine, United States.

Topsham was included in the Lewiston-Auburn, Maine metropolitan New England city and town area.

But a plague, probably smallpox brought by Europeans, decimated the tribe's population in 1615–1616.

On June 16, 1632, the area was granted by the Plymouth Council to Thomas Purchase and George Way, later acquired by Richard Wharton and then, in 1714, by the Pejepscot Company.

[5] Shipbuilding and lumber mills were important early businesses, the latter especially active between 1750 and 1770.

In 1856, the Sagadahoc Agricultural & Horticultural Society erected its building and fairgrounds, and the town remains host to the annual Topsham Fair.

In 1936, a large flood hit Brunswick and Topsham, damaging the pedestrian "Swing Bridge" and causing the Androscoggin to flow through the lower levels of the Pejepscot Mill.

It is thought that Topsham and Brunswick have safe houses related to the Underground Railroad.

These tunnels were constructed of carefully laid red brick with vertical side walls, an arched top and a flat brick-paved bottom up to some 5 feet (1.5 m) wide which would allow the easy passage of individuals on foot as well as a horse and buggy if desired.

It borders the towns of Bowdoin and Bowdoinham to the north, Brunswick to the south, and Durham and Lisbon to the northwest.