Major General Liam Tobin (born William Joseph Tobin; 1895 – 30 April 1963) was an officer in the Irish Army and the instigator of an Irish Army Mutiny in March 1924. During the Irish War of Independence, he served as an IRA intelligence officer for Michael Collins' Squad.
Tobin was born in 1895 Cork, the eldest son of Mary Agnes (nee Butler) and David Tobin, a hardware clerk. Tobin had two younger siblings, Katherine and Nicholas Augustine Tobin, also born in Cork City. Tobin's family moved to John St. in Kilkenny and then to Dublin. Tobin went to school in Kilkenny and was an apprentice in a hardware shop at the time of the 1916 Rising. As a participant in the Easter Rising he fought in the Four Courts Garrison under Edward Daly. He was arrested and courtmartialed. He was sentenced to death and then had his sentence commuted to life imprisonment. He was a prisoner in Kilmainham, Mountjoy, Lewes, Dartmoor, Broadmoor and Pentonville prisons. He was released in June 1917.
Early in 1919, Tobin had become Collins' chief executive in the Intelligence Directorate handling the many spies in Dublin Castle, including double agent David Neligan. Nancy O'Brien worked for Under-Secretary for Ireland James Macmahon, decoding messages sent from London. Each day between 2:30 and 3:30 she would pass any information acquired to either Tobin, Joe McGrath, or Desmond Fitzgerald. Tobin was involved in planning the assassinations of British soldiers, informants, members of the Royal Irish Constabulary, the Dublin Metropolitan Police, and operatives of MI5. He constructed detailed profiles of everyone remotely connected to the British government, often using Who's Who, The Morning Post, and The Times - a newspaper that described him as "one of the most formidable of [the] Twelve Apostles".