| Election Name: | 1859 Iowa Senate election |
| Country: | Iowa |
| Flag Image: | Flag of Iowa (variant).svg |
| Type: | legislative |
| Ongoing: | no |
| Previous Election: | 1857 Iowa Senate election |
| Previous Year: | 1857 |
| Next Election: | 1861 Iowa Senate election |
| Next Year: | 1861 |
| Seats For Election: | 27 out of 43 seats in the Iowa State Senate |
| Majority Seats: | 22 |
| Election Date: | 1859 |
| Party1: | Republican Party (United States) |
| Last Election1: | 22 |
| Seats After1: | 22 |
| Party2: | Democratic Party (United States) |
| Last Election2: | 14 |
| Seat Change2: | 7 |
| Seats After2: | 21 |
| President of the Iowa Senate | |
| Before Election: | Oran Faville |
| Before Party: | Republican Party (United States) |
| After Election: | Nicholas J. Rusch |
| After Party: | Republican Party (United States) |
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. State senators serve four-year terms in the Iowa State Senate.
The general election took place in 1859.[1]
Following the previous election in 1857, Republicans had control of the Iowa Senate with 22 seats to Democrats' 14 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).
Source:[2]
District boundaries were redrawn before the 1859 general election for the Iowa Senate: