The 35-year-old centre-back has played every minute of the Latics' league campaign so far and has scored five goals in all competitions.
Ex-England Under-21 international Clarke joined the club from Bury in July 2016 on a one-year deal.
The Latics sit three places above the relegation places with six games of the season remaining.
Oldham Athletic captain Peter Clarke has signed a new two-and-a-half-year deal with the League One club.