Ó Gnímh was the surname of an Irish brehon family.

The Ó Gnímh family were based at Larne, County Antrim, and were hereditary poets for the O'Neill's and MacDonalds.

The surname is now generally rendered as Agnew.

Notable people with the surname include:

• Eoin Ó Gnímh (fl. 1699), Irish poet and manuscript collector
• Fear Flatha Ó Gnímh (c. 1540–c. 1630), Irish poet

• The family of Ó Gnímh in Ireland and Scotland: a look at the sources, pp. 57–71 in Nomina 8 (1984), Brian Ó Cuív.