The 45-year-old oversaw just nine wins during his tenure, leading to the club’s decision to part ways.
Cambridge United majority owner Paul Barry expressed gratitude for Monk’s efforts during his time at the club.
He said: "We would like to thank Garry for his hard work and commitment to Cambridge United over the last 12 months.
"He really bought into the Club during his time with us and we are all very disappointed that it has not worked out in the way we would all have hoped.
"In the end, the table does not lie and it is the right moment to make a change as we conclude the first part of our football review.
"There are 15 games of this season remaining, and we must continue to fight together to preserve our League One status over the coming weeks.
"At the same time, we will use this period to plan strategically for the next chapter of the Football Club. We will say more about this in the week."