Steakknife (sometimes written as Steak knife or incorrectly as Stakeknife[1]) is the code name of a spy who infiltrated the Provisional IRA, at a high level, as a double agent working for the top secret British Force Research Unit. Reports claim that Steakknife has been working for the British for 25 years.

Steakknife had his own dedicated handlers and agents and it was suggested that he was important enough that MI5 set up an office dedicated solely to him. Rumours suggested that Steakknife was being paid at least 80,000 pounds a year.

Serious allegations have emerged to the effect that innocent lives were sacrificed to protect Steakknife's identity.

On May 11, 2003, several newspapers named Freddie Scappaticci as Steakknife. Scappaticci denies the claims.