Gysbert Van Steenwyk Sr. (birth name: Gijsbert; January 30, 1814 – April 13, 1902) was a Dutch American immigrant, banker, and Republican politician from La Crosse, Wisconsin.

[2] He served as a volunteer in the Royal Netherlands Army in 1830 and 1831, and as a commissioned officer of the National Guards from 1833 to 1849.

Van Steenwyk graduated from the University of Utrecht in 1836, where he studied philosophy and classical literature.

[3][4] Van Steenwyk, at that time was working as a land and insurance agent and living in Kilbourn City (now called Wisconsin Dells), was elected as a Republican member of the Wisconsin State Assembly in 1858[5] for the 1st Columbia County Assembly district (the Towns of Dekorah, West Point, Newport, Lewiston, Portage, Caledonia, Lodi and Pacific) succeeding Democrat Alvin Alden.

He was appointed to the standing committees on education and school and university lands; and on railroads.,[6] then was elected state Bank Comptroller for 1860–61, unseating incumbent Democrat Joel Squires.