Michael Donnellan (1900 – 27 September 1964) was an Irish Clann na Talmhan politician.
Michael Donnellan was born in Dunmore, County Galway in 1900. He joined Sinn Féin after the Easter Rising in 1916. Donnellan served as a member of Galway County Council from 1927 until 1945, originally as a member of Fianna Fáil.
Donnellan became disenchanted with the party in the mid-1930s, as did many supporters in the province of Connacht. He became involved in talks with a number of farmers in order to create a new Farmers' Party. The original group was known as the Irish Farmers Federation, however it split shortly afterwards between the larger more conservative farmers and poorer more radical farmers from the West over the issue of de-rating. Donnellan led the radical faction, which founded Clann na Talmhan in 1939. In 1940 a by-election was called in the Galway West constituency and his supporters persuaded him to stand. Fine Gael stood aside hoping to inflict damage on Fianna Fáil, which won, though Donnellan secured almost 30% of the votes cast. He was elected to Dáil Éireann as a TD for Galway West at the 1943 general election.
Donnellan, however, proved too radical for the party members from the province of Leinster, due to his more left-wing leanings and his support for land agitation during the mid-1940s. He was soon replaced as party leader by conservative Mayoman Joseph Blowick. Donnellan's decision to abstain on Éamon de Valera's nomination for Taoiseach in 1943 led some to suspect he had done so out of loyalty to his old party leader. Donnellan served as a Parliamentary Secretary to the Minister for Finance on two occasions with responsibility for the Office of Public Works.
In his youth Donnellan was a talented footballer who won All-Ireland medals with the Galway Senior football team in the 1920s and 1930s. He died in Croke Park at the 1964 All-Ireland final, shortly before his son John Donnellan, as victorious Galway captain, received the Sam Maguire Cup. The subsequent by-election was won by John, standing as a Fine Gael candidate.
His grandson, Michael Donnellan also won All-Ireland medals with Galway in 1998 and 2001.