Thornton is one of a select group of jockeys to have ridden over 1,000 jumps winners and also won the Cheltenham Gold Cup on Cool Dawn in 1998.
Having began his career with Arthur Stephenson, Thornton enjoyed big-race success on the likes of See More Business, French Holly, The Listener and Miko De Beauchene.
In recent years Thornton has struggled with injury, he even damaged his knee on dismounting after riding his 1,000th winner with the injury keeping him out of the saddle for months.
“I’m finally hanging the boots up on Wednesday,” said the North Yorkshire jockey.
“I woke up on Thursday morning, had a few things running around in my head and I thought the time was right. It was as simple as that.
“I had a winner for Seamus (Mullins) at the start of the season, he’s having a good run of things but I’m not getting as many rides as I used to and I just felt I had to grow up. Father Time is catching me up and I’d like to do it on my own terms.
“I’m looking forward to Uttoxeter - it’s the right time for me, the right time for Seamus and time moves on, he’s got his owners to think about.
“I’ve got a lot to look back on.
“I rode my first winner on Wrekin Hill on November 22 in 1991, he was a cracking horse for me to get started on. I rode my first three winners on him. I owe WA (Stephenson) everything, I wouldn’t be where I am now without him.
“My wife asked me this morning if I was sure, but I absolutely am, I’ve no regrets. People talk about the end of an era, but I’ve probably spanned two eras.
“I’ve got four rides but even if one of them wins, I will be riding the fourth, simply because I love it.”