Joyce only took charge of the Latics in November 2016, and departs having led the team to just five wins from their 22 Championship matches, suffering 12 defeats in the process.
"It is unfortunate that we have made this decision but with the team in such a perilous position in the league, we need to act now because we cannot afford to fall any further behind," Sharpe told the club's official website.
"Warren was appointed with the future in mind in terms of developing players but preserving our Championship status is the absolute priority and we have a duty to do whatever gives us the best chance of doing that.
"Results and performances have simply not been up to standard often enough in recent matches and although we acknowledge the difficulties faced in managing a team in a league where we are competing against clubs with much larger budgets, the nature of some of our recent defeats, especially against close rivals, has fallen short in terms of what we as a club, and all our supporters, expect."
Assistant manager Graham Barrow has been made interim manager for the remainder of the season.