The Shamrock Shake is a seasonal green mint flavored milkshake dessert sold at some McDonald's restaurants during March to celebrate St. Patrick's Day in the US, Canada and Ireland.

[4] Shamrock Shakes are sold at select U.S.[5] and Canadian stores during the months of February and March,[3] as well as in Ireland.

[8][9] Starting in 1975, McDonald's used the Uncle O'Grimacey character (a relative of Grimace who came to visit in March) to market Shamrock Shakes.

[10] According to Bryan Bierman in a PhillyVoice article written in 2017, the character was phased out due to having "controversial ties with the IRA.

[13] In 2025, McDonald's would bring back the Uncle O'Grimacey character, as well as offer the Shamrock Shake in the UK for the first time.