Sir Michael Francis O'Dwyer GCIE KCSI (28 April 1864 – 13 March 1940) was an Irish colonial officer in the Indian Civil Service (ICS) who served as the Lieutenant Governor of the Punjab from 1913 to 1919. His tenure is widely remembered for the 1919 Jallianwala Bagh massacre in Amritsar.

During O'Dwyer's tenure as Punjab's Lieutenant Governor, the Jallianwala Bagh massacre occurred in Amritsar, on 13 April 1919. As a result, his actions are considered among the most significant factors in the rise of the Indian independence movement. O'Dwyer endorsed Reginald Dyer's action at Jallianwala Bagh and made it clear that he considered Dyer's orders to shoot at the crowds was correct.

He subsequently administered martial law in Punjab, on 15 April and backdated it to 30 March 1919. In 1925, he published India as I Knew It in which he wrote that his time as administrator in Punjab was preoccupied by the threat of Indian Nationalism, demanding freedom and the spread of political agitation. In 1940, in retaliation for the massacre, O'Dwyer was assassinated by the Indian revolutionary Sardar Udham Singh.

Michael Francis O'Dwyer was born on 28 April 1864 in Barronstown, Limerick Junction, County Tipperary, to John, a landowner of Barronstown, Solohead, and Margaret (née Quirke) O'Dwyer, of Toem, both in County Tipperary, Ireland. He was the sixth son in a family of fourteen children, At the age of seven, he was sent to be schooled at St Stanislaus College, Rahan, County Offaly.

Later, he attended Mr Wren's educational crammer school in Powis Square, London, and subsequently passed the open entrance competition for the Indian Civil Service in 1882. After completing two years of probation at Balliol College, Oxford, he passed the final examination in 1884 in fourth place overall. At the time, the ICS examination was highly competitive, with no more than 1200 ICS officers in office at one time, and he was likely influenced by the reputations of the likes of Lord Lawrence, one of the first British civil administrators in India. In his third year he obtained a first class in jurisprudence. Philip Woodruff wrote of O'Dwyer's upbringing:

Michael O'Dwyer was one of the fourteen children of an unknown Irish land-owner of no great wealth, as much farmer as landlord. He was brought up in a world of hunting and snipe-shooting, of threatening letters and houghed cattle, where you were for the Government or against it, where you passed every day the results of lawlessness in the blackened walls of empty houses. It was a world very different from the mild and ordered life of southern England... One gets the impression [of O'Dwyer when at Balliol] of a man who seldom opened a book without a purpose, whose keen hard brain acquired quickly and did not forget but had little time for subtleties.

The O'Dwyer family were Anglophiles and Unionists. In 1882, his family home in Ireland was fired upon by Irish nationalists, and the following year, his father died after a second stroke. Of his siblings, two brothers served in India, and two others became Jesuit priests.

In 1885, he travelled to India as an ICS officer and was first posted to Shahpur in Punjab. He distinguished himself in land revenue settlement work and in 1896 was made director of land records and agriculture in Punjab. Subsequently, he was placed in charge of the settlements of Alwar and Bharatpur states.