The Unionist Party of Northern Ireland was a political party founded by Brian Faulkner in September 1974.

The party emerged following splits in the Ulster Unionist Party in 1974 over the Sunningdale Agreement. Faulkner had led the UUP into a power-sharing coalition but in January 1974 he was deposed as leader as the anti-Sunningdale faction of the party won control. In the February 1974 general election a number of Faulkner's followers (including several sitting MPs) stood as "Pro Assembley Unionists" againsty a coalition of the Ulster Unionist Party, the Vanguard Progressive Unionist Party and the Democratic Unionist Party. They failed to win a single seat at Westminster, and this defeat contributed to the downfall of the power sharing Executive established by Sunningdale. However they remained active and in September constituted themselves as the Unionist Party of Northern Ireland, committeed to a return to powersharing as a settlement for Northern Ireland.

The party did not prosper. In the October 1974 general election they again failed to make much ground. Then in the 1975 elections to the Northern Ireland Constitutional Convention they won only a handful of seats, compared to a substantial block of anti-powersharing Unionists. As a result the influence of both the UPNI and Faulkner waned.

Faulkner died in a riding accident in 1977 amd was succeeded as leader by Anne Dickson, the first woman to lead a political party in Northern Ireland. However the party continued to make little ground, especially as the Alliance Party of Northern Ireland gained momentum as a party committed to power sharing and the maintenance of the Union. As a result in 1981 the UPNI was formally dissolved.