Mill Brook is a watercourse, about 3 miles (4.8 km) long, in Massachusetts, United States.

[3] On the afternoon of April 19, 1775, during the first hours of the American Revolutionary War, it was on a bridge over Elm Brook, a tributary of Mill Brook, at Meriam's Corner that British regulars were fired upon for the first time by colonial militia during their retreat from Concord to Boston.

[3] Route 2 was constructed across the highest headwaters, separating the brook from the lower section.

[3] In 1977, Richard T. T. Forman described the brook as "one of the most degraded streams in Concord", with channelization, wetland drainage and the scarcity of fish all being contributing factors.

The cold is merely superficial; it is the summer still at the core, far, far within.Poet William Ellery Channing wrote The Mill Brook:[6] I like the maples on my side, Dead leaves, the darling trout; Laconic rocks (they sometime put me out) And moon or stars that ramble with my tide;