He started practising at Queen's on Saturday but this was the first time he has set foot on Centre Court
since lifting the trophy 12 months ago
, and he looked far from happy with the surface.
Two break points went begging in the opening game as the Scot slid around the back-court and the conditions seemed to hamper his movement and intensity.
The 25-year-old had no answer when Mahut raised the pace to devastating effect in game six.
A forehand on to the line helped the Frenchman engineer his first break point and although he wasted that opportunity, a second was converted with a ruthless cross-court forehand.
Jonathan OverendBBC tennis correspondent
"Nicolas Mahut was a very difficult first-round opponent for Andy Murray. The Frenchman is so comfortable on the grass with his serve-volley game. It used to mean so much that a good week at Queen's would set you up for Wimbledon. All England Champions would endlessly come from here, but that is less so these days. This is no time for panic stations. Andy Murray will still get more grass-court matches in before Wimbledon and, even though he would have dearly loved to have defended his title, I don't think he will be desparately disappointed."
Mahut consolidated his strike with a hold to love and took control of the match with an ace on set point.
Murray put a backhand long to give Mahut a break point at the beginning of the second set but the British number one scrambled through before two double-faults gifted him a 2-0 lead.
A backhand floated wide though to relinquish that break in the fifth game though and a tie-break was require to separate the pair.
Murray's class and experience eventually told in the shoot-out, chasing down a drop shot to flick a majestic backhand across Mahut to level.
Interview: Andy Murray
A double-fault in game one of set three handed Murray the early initiative, but it was passed straight back when the world number four sent a lob wide on.
After uttering an expletive and repeatedly banging his racquet against his head, Murray regained his composure yet he could not take advantage of a break point in game five as Mahut stood firm.
Another tie-break beckoned but it was a one-sided affair this time as four Murray errors gave Mahut six match points, the second of which he took when Murray sliced a backhand into the net.
British number three
also came unstuck against French opposition - although his defeat at the hands of the world number five Jo-Wilfried Tsonga was less of a surprise.
Baker, ranked 203rd in the world, gave a good account of himself, matching Tsonga from the baseline at times, but eventually slipped to a 6-3 6-2 defeat in 57 minutes.
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