Ray Floyd sank a routine one-foot putt on the fourth sudden-death playoff hole yesterday to beat Craig Stadler and win golf's richest tournament, the Million Dollar Challenge in Sun City, Bophuthatswana.

Stadler missed a 2 1/2-foot putt before Floyd holed out for par to collect the $300,000 first prize. Stadler, the leading money-winner on U.S. tour this year, won $150,000.

Stadler forced a playoff on the final hole of regulation when he reached the edge of the green from the side of a television scaffolding 170 yards away. He and Floyd each two-putted the 18th for pars, finishing the round with one-under 71s for a four-round total of eight-under 280.

Floyd appeared to have the playoff won on the green of the par-5 14th, the first of the sudden-death holes. He came out of the sand to within inches of the cup for a birdie. But Stadler made a 22-foot putt to continue the playoff.

They both parred the next two holes before Stadler got himself in trouble on the par-4 17th when his shot from the fairway rough glided over the pin and rolled into the crowd. Floyd's second shot landed on the green, a hilly 50 feet from the cup.

Floyd putted to within a foot of the hole, while Stadler hit a chip shot to within 2 1/2 feet. But Stadler's putt rimmed the hole and rolled out before Floyd made his putt to end the tournament.

Third place went to Lee Trevino, who came from far behind to shoot a 67 and end the tournament seven under at 281. He won $105,000. Jerry Pate had led the tournament by two strokes going into the final round. But he shot an 80 and tied for sixth with Spain's Seve Ballesteros, who led after two rounds. Each finished at 286 to win $63,500 apiece . . .

In Acapulco, Jose Canizares caught Spanish teammate Manuel Pinero with a 33 to tie for the individual lead with nine holes left to play in the 29th World Cup. Pinero made the turn in 34, increasing Spain's lead over second-place United States to 12 shots . . .

In Palm Beach Gardens, Fla., Don January shot a two-under 70 for a four-day total of 288, rallying from four strokes back of the leaders for his second PGA seniors title on the National Golf Club Champion Course.