has chosen to return to the ranks at Worcestershire, after five years as the captain.
Leach will lead his side for the final time this week, when Worcestershire take on Leicestershire in their final LV=Insurance County Championship match of the season, starting at New Road on Tuesday.
Although he is likely to finish as his county's leading Championship wicket-taker for 2021, with a current tally of 32 at 33.68, it has been a tough campaign for the club, who are lying fourth in the third division, having missed out on the knock-outs in both the 50- and 20-over competitions.
"I have decided to stand down as club captain," Leach said. "It's obviously been a very tough one, one that has been on my mind for some time, if I'm honest.
"I made the decision just before the home game with Sussex three weeks ago that this was going to be my final season as captain.
"It was a difficult decision to make, but one that I feel is right, not only for myself but also for the group as well.
"I've done it for five years, and I'm immensely proud of what I've managed to achieve in some difficult times for the club over that five years.
"I've had a lot of things to deal with on and off the field, and now I guess the time is right to focus on my cricket and getting back to really enjoying it and doing the best I can with the bat and the ball."
Leach took over as captain from Daryl Mitchell at the end of the 2016 season and led the side to promotion in the County Championship 12 months later, thanks in no small part to his own haul of 69 wickets, as well as the semi-finals of the Royal London Cup.
"That last day against Durham when we went up as champions [in 2017] was definitely the highlight from a personal point of view and holding the Division Two trophy aloft at New Road.
"I've given everything to this club as a player pre-captaincy and, as captain, I've done exactly the same. I've led the club with immense pride and done my best every single day. That is how I will continue to operate as a cricketer."
Worcestershire's head coach, Alex Gidman, paid tribute to Leach, who has taken 326 first-class wickets and scored 3,284 runs to date in his career.
"Joe has decided to stand down as captain of the club," Gidman said. "His efforts as a captain have been of the highest order, and he has led the team through some very challenging times and has done an exceptional job.
"He should be very proud of his efforts, and I'm sure he will look forward to some more successful years as a bowling all-rounder for us.
"I know he will put a lot of effort into, firstly, his cricket, which is really important and, secondly, he will get right behind whoever the next captain is and still do a very job as a senior player.
"There is no doubt he has still got a huge amount to offer us. He is still a very big part of the plans and a great man for us to have around still."
Worcestershire Cricket Steering Group Chairman, Paul Pridgeon, said: "Joe has been a fantastic servant of the club and has done a terrific job as captain over the last five years.
"He has grown into the job, is an excellent ambassador for the club and the players under his control."