"Gladiator" Oscar nominee Joaquin Phoenix has checked himself into a rehabilitation clinic to be treated for alcoholism.

The 30-year-old actor - whose brother River Phoenix died from a drug overdose in 1993 aged 23 - entered the clinic voluntarily, reports the Internet Media Database.

His spokesperson said: "He was uncomfortable with the way he was living his life and found the courage to deal with the disease".

The actor plays late country legend Johnny Cash opposite Reese Witherspoon in the upcoming biopic "Walk The Line", set for release later this year.