Reaching the last four had exceeded many people's expectations for Murray, although he insisted not his own, but he appeared to completely run out of steam.
Nadal was never under the slightest pressure and Murray won just 10 points on his opponent's serve in a 6-3 6-2 6-1 loss that lasted just an hour and 40 minutes.
There was no disguising the size of the task that faced Murray when he walked out onto Court Philippe Chatrier.
Nadal had lost just one of his 65 matches at Roland Garros and none of the last 33.
He had beaten Murray in straight sets when they met in the last four here three years ago, while the Scot had only beaten one top-10 opponent on clay in his career.
Murray had also spent four and a half hours longer on court than Nadal having played his first two five-set matches since back surgery.
For the first time all tournament it was hot and sunny, the conditions Nadal loves best, and it was the Spaniard who made a flying start.
Murray won a 22-shot rally on the first point but quickly found himself 3-0 down before steadying the ship to hold serve.
The pair had met for the first time in nearly three years in Rome three weeks ago, and Murray very nearly emerged victorious.
On that occasion he had blitzed Nadal in the first set but the conditions were cold and damp, helping Murray push the Spaniard back.
It was the British number one doing most of the chasing this time, and he could not find a way back into the set, Nadal serving out with ease.
Nadal's forehand, the extreme topspin sending the ball spitting off the clay, was simply ferocious.
The Wimbledon champion had hit his backhand with stunning power and timing in the previous two rounds but he did not seem to have enough energy to wrest any form of control away from Nadal.
The world number one was playing superbly and a Murray forehand wide gave him a break for 2-1 in the second set.
Nadal had revealed earlier in the tournament that the back pain that so compromised him in the Australian Open final against Stan Wawrinka had returned, forcing him to take some pace off his serve.
But there was nothing wrong with his serve on Friday, Murray managing just six points against it in the first seven games.
Nadal was winning so comfortably that the atmosphere was completely flat, and the top seed moved further ahead with another break for 5-2.
That quickly became a two-set lead as Nadal served out to love.
Murray's hopes of a comeback appeared to be virtually nil, and even more so when Nadal broke serve once more for 2-1.
The crowd felt the need to generate their own entertainment with a Mexican wave that held up play for a good couple of minutes.
Murray could have been forgiven for just wanting the torture to end as quickly as possible, and Nadal moved closer with another break to lead 4-1.
Murray tried desperately to hold onto his serve one more time but to no avail, Nadal clinching victory on his first match point with a simple smash.