John Blackadder

John Blackadder or Blackader may refer to:
 * John Blackadder (preacher) (c. 1622–1685), Scottish Covenanter
 * John Blackadder (soldier) (1664–1729), Scottish soldier, son of the preacher
 * Sir John Blackadder, 1st Baronet (1626–c. 1670), of the Blackadder baronets