Stocker calls time as RGT director.
Since 2001, Stocker has been integral to the charity's ongoing success of homing retired greyhounds during often very difficult economic times.
Last year the RGT celebrated homing its 50,000th greyhound. Prior to that in 2009, the Trust homed a record 4,700 greyhounds.
Throughout his time at the helm Stocker has sought to increase the appeal of retired greyhounds to the general public, showcasing what great pets they make and how easy they are to look after.
He was the driving force behind creating the Great Greyhound Gathering - now in its fourth year, drawing thousands from around the country to its home at Nottingham Racecourse - and launching the Greyhound Extravaganza last year in Suffolk.
Commenting on the announcement, Dr Andrew Higgins, chair of the RGT, said: "I'd like to thank Ivor for all his hard work over the years. I know that our 70 or so branches - and hundreds of volunteers - throughout the country have benefitted from his unstinting desire to assist them finding homes for these lovely dogs.
"He has helped the charity develop and increase its profile, and has been instrumental in laying strong foundations for our future growth."
A replacement will be sought.
Ivor Stocker: retiring after ten years