Opening bat Billy Godleman is to leave Derbyshire at the end of the season after 11 years with the club.
The 34-year-old scored more than 10,000 runs for them after joining from Essex and was captain from 2016 to 2022.
Godleman had a lean summer last year, before scoring 158 at the end of the season against Leicestershire.
He has only played three Championship games this season, in part due to the run-scoring consistency of the Luis Reece-Harry Came partnership.
Godleman made a career-best score of 227 for Derbyshire against Glamorgan in 2019, one of four centuries in his most successful season, when he made 1,087 runs.
The club have confirmed that Scotland spinner Mark Watt, Sri Lanka paceman Suranga Lakmal, batter Tom Wood and all-rounder Archie Harrison will also leave at the end of the summer.
Next year's T20 World Cup clashes with the domestic T20 Blast, which Derbyshire say would limit Watt's availability.
All-rounder Mattie McKiernan, meanwhile, has decided to retire from professional cricket.
The 29-year-old played eight first-class games, 17 in List A cricket and 42 T20 games.
"He will now look towards a career in coaching, where he will aim to provide valuable knowledge of the professional game to the next generation of upcoming players," said a club statement.