UPDATE 1-Olympics-Swimming-Phelps wins eighth Olympic gold

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By Julian Linden

BEIJING, Aug 17 (Reuters) - Michael Phelps won his eighth gold medal at the Beijing Olympics on Sunday, breaking fellow swimmer and compatriot Mark Spitz's 1972 record of seven golds at a single Games.

The 23-year-old American had already won more gold medals than any other athlete at the Olympics.

"I don't know what to feel, so many emotions, so much excitement. I just want to see my mum," he said.

"Its been nothing but an upwards rollercoaster but its been nothing but fun."

Spitz's record had stood unchallenged for 36 years but the wait to find someone to go better than Phelps could take another century.

"The biggest thing is nothing is impossible," he said.

"With so many people saying it couldn't be done, all it takes is an imagination.

"That's something I learned, something that helped me."

His eighth gold medal came in the 4x100 metres medley relay, the final event of the Olympic swimming programme, and was accompanied by another world record.

Phelps teamed up with backstroker Aaron Peirsol, breaststroker Brendan Hansen and freestyler Jason Lezak to help the United States smash the old mark of three minutes, 30.68 seconds with a winning time of 3:29.34.

It was the seventh world record Phelps has been involved in at the Water Cube but more significantly it provided him with an eighth gold medal.

He had earlier won the 400 individual medley, 4x100 freestyle relay, 200 freestyle, 200 butterfly, 4x200 freestyle relay, 200 individual medley and 100 butterfly.

Coupled with his six golds from Athens in 2004, Phelps is a runaway leader on the all-time list of gold medallists, having taken his tally to 14.

Spitz, American athlete Carl Lewis, Finnish runner Paavo Nurmi and Soviet gymnast Larysa Latynina, all finished their careers with nine golds.

(Editing by Greg Stutchbury)