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Denis Gallagher (Irish: Donnacha Ó Gallchobhair, 23 November 1922 – 4 November 2001) was a senior Irish Fianna Fáil politician. He served as Minister for the Gaeltacht on two occasions.

Denis Gallagher was born in Currane, by Clew Bay, facing Achill Island, County Mayo in 1922. He was educated locally and at St. Enda’s College in Galway. He qualified as a national school teacher having graduated from St. Patrick’s Drumcondra in Dublin. He taught in Drimnagh in Dublin for several years before returning to Mayo in 1946 to take up a teaching post. Gallagher stood as a Clann na Poblachta candidate in the 1954 General Election in Mayo but failed to be elected.

In the 1960s Gallagher changed allegiance and became a member of Fianna Fáil. He was elected to Mayo County Council in 1967 and was elected to Dáil Éireann on his second attempt in the 1973 general election for the Mayo West constituency. Gallagher did not remain on the backbenches for very long. He joined the Fianna Fáil front bench in 1974 as spokesperson on Fisheries. He remained in that position until 1977 when the party returned to power and Gallagher was appointed Minister for the Gaeltacht. He was an active Minister with an interest in Irish language affairs.

During the 1979 leadership contest Gallagher supported George Colley. However, Charles Haughey became party leader and Taoiseach. Because of this Gallagher was demoted to the position of Minister of State. In October 1982, following the resignations of Martin O'Donoghue and Desmond O'Malley from the Cabinet, after they supported Charlie McCreevy’s motion of no confidence, Gallagher returned as Minister for the Gaeltacht. He remained in that post until December when Fianna Fáil went into opposition.

Following the 1987 general election there was no place in the cabinet for Gallagher. He was however made Minister of State at the Department of the Gaeltacht. As a result he retired from politics at the following general election in 1989. After his retirement he worked to advance the Irish language cause and also served as chairman of the Gaelic Athletic Association in Mayo.