In the 1885 Iowa State Senate elections Iowa voters elected state senators to serve in the twenty-first Iowa General Assembly.

Elections were held in 24 of the state senate's 50 districts.

The general election took place on November 3, 1885.

To claim control of the chamber from Republicans, the Democrats needed to net 15 Senate seats.

Republicans maintained control of the Iowa State Senate following the 1885 general election with the balance of power shifting to Republicans holding 31 seats and Democrats having 19 seats (a net gain of 8 seats for Democrats).