A statement said the woman went to deputies last Tuesday and told them the "sexual misconduct" occurred in the Edwards area of the county the previous night.
"Upon review of interviews and physical evidence, investigators met with the District Attorney's office and concluded they had enough evidence to charge Kobe Bryant with felony sexual assault," the statement said.
It added that Bryant, 24, was co-operating with police and had voluntarily complied with an arrest warrant by turning himself in and posting a $25,000 bond on July 4. The statement said county sheriff Joseph Hoy would hold a news conference Monday.
LAKERS CORNERSTONE
Bryant has been the cornerstone, along with Shaquille O'Neal, of the Lakers, the three times National Basketball Association champion between 2000-02.
He joined the team in the 1996-97 season and the following year was the youngest player ever, at the age of 19, to be selected to an All-Star team.
Bryant has been an All-Star ever since and was MVP (Most Valuable Player) of the 2002 Game.
He was the NBA's second-leading scorer last season, averaging a career-best 30 points while playing in all 82 games for the Lakers. He collected 40 or more points in nine straight games in February.
Bryant also had career-high averages of 6.9 rebounds and 5.9 assists last season.
The Lakers were eliminated from the Western Conference semi-finals by the eventual NBA champion San Antonio Spurs.
Bryant underwent shoulder surgery in New York on June 12 but is expected to be ready for the start of training camp in October.
The 24-year-old has been married to Vanessa Laine since April 2001. The couple had their first child, Natalia Diamante Bryant, in January.
Bryant is the son of former NBA player Joe "Jellybean" Bryant.
