Oran Faville[c] Republican Nicholas J. Rusch[d] Republican In the 1859 Iowa State Senate elections, Iowa voters elected state senators to serve in the eighth Iowa General Assembly.

Following the expansion of the Iowa Senate from 36 to 43 seats in 1859, elections were held for 27 of the state senate's 43 seats.

To claim control of the chamber from Republicans, the Democrats needed to net eight Senate seats.

Republicans maintained control of the Iowa State Senate following the election with the balance of power shifting to Republicans holding 22 seats and Democrats having 21 seats (a net gain of 7 seats for Democrats).

[a] Source:[11] District boundaries were redrawn before the 1859 general election for the Iowa Senate: