Eric "the Eel" Moussambani's chances of competing at the Athens Olympics have been scuppered by problems over his application form.
Moussambani is now pondering retirement
Officials were unable to locate his passport photograph, preventing him from competing for Equatorial Guinea.
Moussambani attracted worldwide attention when he struggled to last place in his 100m freestyle swimming heat at the Sydney Games in 2000.
His time was eight seconds off that of Ian Thorpe in the 200m.
As a result of missing out on Athens, Moussambani said he was considering retirement.
He told the Sydney Morning Herald: "I would like to continue swimming, but I don't know if I can right now.
"People wanted to see me back. People wanted to see me in Athens."
He told the Spanish media that he had improved dramatically since Sydney and had wanted people to see him as a "real swimmer".
"It's a terrible thing they've done to me. It makes me angry because I was training to be in Athens," he was quoted as saying.