Lilia Osterloh (born April 7, 1978 in Columbus, Ohio) is a tennis player from the United States, who started a professional career in August 1997. She reached her highest individual ranking in the WTA Tour in April 23, 2001, when she became World No. 41. Osterloh was eliminated in the quarterfinals of the women's tournament at the 1999 Pan American Games in Winnipeg, Canada, after losing to eventual gold medalist María Vento-Kabchi from Venezuela.

Osterloh attended Stanford University for one year during the 1996-1997 season, starting as a freshman at the team's #3 singles position and ending the season at the #1 singles position, compiling a 30–3 overall singles record. She also played doubles at the team's #1 doubles and #2 doubles positions. She then won the 1997 Division I NCAA Women's Tennis Championship in singles with a 6–1, 6–1 victory over Florida's freshman M.C. White and led her team to the 1997 NCAA team championship over Florida 5–1, Stanford's ninth team title. She was named All American in both singles and doubles and was Tennis magazine/Rolex College Player of the Year for 1997. After winning the NCAA championship, she earned a berth into the 1997 US Open women's singles main draw and decided to leave Stanford and turn professional.

1. Serena Williams (1 ▬) 2. Venus Williams (4 ▬) 3. Melanie Oudin (43 ▲1) 4. Vania King (74 ▬) 5. Bethanie Mattek-Sands (76 ▲6)