Sigmund von Erlach (October 3, 1614 – December 7, 1699; sometimes given as "Sigismund von Erlach") was a Swiss military commander and a politician of Bern.
A member of the von Erlach family, one of the foremost families of the city of Bern, von Erlach initially pursued a military career as a mercenary commander, first in the services of Bernhard of Saxe-Weimar and later in France.
At his return to Bern in 1645, he became a member of the canton's Grand Council and seven years later, a member of the city council (Kleiner Rat).
Sigmund von Erlach commanded the Bernese troops in the Swiss peasant war of 1653, putting down the rebellion of the rural population with force.
He also commanded the troops of Bern in the First war of Villmergen, a religiously motivated civil war in the Old Swiss Confederacy that the Protestant cantons lost.
Although he was criticized heavily for his failure in this conflict he continued his political career in Bern, which culminated in 1675 with his election to the post of Schultheiss (mayor).