Harriet Harman's second Shadow Cabinet was formed by Harriet Harman in 2015 during her second period as Acting Leader of the Labour Party. She assumed this role after Ed Miliband resigned as party leader and announced she would continue until a new leader was elected on 12 September 2015. Miliband's resignation followed the party's defeat at the 2015 general election.

The Leader of His Majesty's Most Loyal Opposition, more commonly referred to as the Leader of the Opposition, is the person who leads the Official Opposition in the United Kingdom. The position is seen as the shadow head of government of the United Kingdom and thus the shadow prime minister of the United Kingdom.