William Lee Plunket, 5th BaronPlunket, GCMG, KCVO, KBE (December 19, 1864 – January 24, 1920) was a British diplomat and administrator.
Having succeeded his father as fifth BaronPlunket in 1897, Plunket three years later became private secretary to Lord Cadogan, Lord Lieutenant of Ireland at the time, and fulfilled the same role for his successor, Lord Dudley.
Lord Plunket died aged 55 in London, and was buried in the city's Putney Vale Cemetery.