Joseph P. McGuinness (10 April 1875 – 31 May 1922) was an Irish Sinn Féin politician who was elected as Member of Parliament (MP) for South Longford at by-election in 1917.
He was re-elected as MP for the new Longford constituency at the 1918 general election.
McGuinness was serving a term in prison when he was elected to Westminster and among those who worked on his election campaign was Michael Collins. The election slogan for McGuinness at the time was "Vote him in to get him out!"
In common with the other Sinn Féin MPs, he did not take his seat in the British House of Commons, sitting instead as a TD in the revolutionary First Dáil, where he was appointed as Director of Trade and Commerce on 27 October 1919.
He was re-elected unopposed at the 1921 general election in the new Longford–Westmeath constituency; he died before the 1922 general election. He voted in favour of the Anglo-Irish Treaty in January 1922.
At a subsequent by-election, his seat was taken by his brother Francis McGuinness.