Mill Brook may refer to:

• Mill Brook, Shropshire, a tributary of the River Rea, Shropshire in England

• Mill Brook (Swift River tributary), a tributary of the Swift River in New Hampshire
• First River, formerly known as Mill Brook, a tributary of the Passaic River in New Jersey
• Mill Brook (Pepacton Reservoir tributary), a river in Delaware and Ulster Counties, New York
• Mill Brook (Unadilla River tributary), a river in Chenango County, New York
• Mill Brook (West Canada Creek tributary), a river in Herkimer County, New York
• Mill Brook community, historic community in Vermont

• Mill Creek (disambiguation)
• Millbrook (disambiguation)