The team will conduct an "immediate search" to replace Ireland.
"I want to personally thank Jeff for his hard work and dedication in building the team over the past six years," owner Stephen Ross said in a statement. "After a series of discussions, we both felt that it was in our mutual best interest to part ways. Jeff was a loyal and dedicated member of the Dolphins and we wish him and his family nothing but the best."
NFL Media's Jeff Darlington reported, via sources, that Ireland was going to be stripped of power if he remained with the organization, leading to the mutual decision to end the partnership.
Ireland took over operations in 2008, and was a driving force in the team's improvement from 1-15 to 11-5 and an AFC East title that season. The Dolphins missed the playoffs in the five seasons that followed, however, and Ireland became a hugely unpopular figure amongst the fan base.
The Dolphins started 3-0, but uneven play and an ugly bullying scandal involving offensive linemen Richie Incognito and Jonathan Martin darkened the landscape. A Week 15 win over the Patriots put the Dolphins at the doorstep of the postseason, but ugly back-to-back losses left them at 8-8 and out of contention.