Daryl Jacob will partner Pineau De Re when the horse goes in search of back-to-back victories in the Crabbie's Grand National on Saturday week.
Leighton Aspell steered Dr Richard Newland's 12-year-old to Aintree glory 12 months ago, but is unavailable after trainer Oliver Sherwood confirmed Many Clouds an intended runner in the world's most famous steeplechase.
Jacob, who won one of the most thrilling Grand Nationals of all time aboard the Paul Nicholls-trained Neptune Collonges three years ago, rode Pineau De Re when he finished down the field over hurdles at Cheltenham earlier this season.
Owner John Provan said: "We spoke to Leighton on Saturday and he's going to ride Many Clouds, so we've booked Daryl Jacob to ride our horse.
"Daryl is a top-class jockey and was Richard's main rider until he got the big job with Paul Nicholls a while back.
"We then used Sam Twiston-Davies quite a lot until Paul Nicholls also spotted him and Sam replaced Daryl.
"We've always thought a lot of Daryl and he's a Grand National-winning jockey. He has plenty of experience riding in the race, which counts for a lot.
"Daryl will come and school the horse this week and we'll see if he can go and win back-to-back Grand Nationals, which would be quite an achievement."
Jacob is unsurprisingly excited about getting the leg-up on the defending champion.
He said: "It's obviously very exciting to be riding last year's winner.
"At the start of the season I was riding quite a few for Richard and I rode this horse over hurdles at Cheltenham.
"It's a big advantage to be riding a horse who has been around Aintree before, and it's an even bigger advantage to be riding a horse who's won there before.
"I'm going to have a sit on him on Wednesday morning, which will be great, and I'm really looking forward to riding him.
"I think it's a really open Grand National this year and he must go there with as a good a chance as any of them.
"I'll be going there full of confidence."
Sherwood and owner Trevor Hemmings had been keen to delay the Many Clouds call after his slightly disappointing run in the Cheltenham Gold Cup earlier this month, but the decision has now been made to compete on Merseyside.
Sherwood said: "He's an intended runner in the National.
"A lot can happen in the next fortnight, but we've not done a lot with him since the Gold Cup and that is the plan.
"There's nothing else for him, but I've always thought he would be a National horse at some stage.
"It was a teamwork decision (to run him in the National). He did his first bit of light work on Saturday and we were very happy with him.
"It has always been a dream for Mr Hemmings and whether we've made the right decision, time will tell."
