Adam Mikolaj Sieniawski (1666–1726) was a Polish nobleman, aristocrat and military leader.
He was the son of Hetman Mikolaj Hieronim Sieniawski and Cecylia Maria Radziwill, daughter of Court and Grand Marshal Prince Aleksander Ludwik Radziwill.
He married Elzbieta Lubomirska, daughter of Court and Grand Marshal Prince Stanislaw Herakliusz Lubomirski, in 1687.
Sieniawski was voivode (governor) of Belz Voivodeship from 1692 to 1710, Field Crown Hetman since 1702, Great Crown Hetman since 1706, Castellan of Kraków since 1710 as well as starost of Lviv, Rohatyn, Lubaczów, Stryj and Piaseczno.
In 1697 he supported François Louis, Prince of Conti as candidate for king of Poland but accepted the election of Augustus II.
As commander of the Sandomierz Confederation, he thwarted the attempt to unite forces of Stanislaw Leszczynski with them of Charles XII of Sweden.
Later, in opposition to King Augustus II.Like his father he participated in the Vienna expedition of 1683.
He commanded the left wing of Polish forces at the Battle of Vienna.