Tennys Loren Sandgren II (/ˈtɛnɪs ˈsændɡrən/ TEN-iss SAND-grən; born July 22, 1991) is an American former professional tennis player. He has achieved a career-high ATP singles ranking of No. 41 on January 14, 2019. He played two years of college tennis at the University of Tennessee before launching his professional career.

Sandgren's parents, South African Lia Lourens and American David Sandgren, met at a tennis club in Johannesburg. They married and moved to Tennessee in 1988 with Sandgren's older brother, Davey. Davey Sandgren was also a tennis player who achieved a career-high ATP ranking of 800 in doubles in 2009.

Sandgren, who was named Tennys after his Swedish great-grandfather, was home-schooled and was coached by his mother. He started playing tennis at age five.

As a junior, Sandgren compiled a singles win–loss record of 70–38 (and 53–35 in doubles), reaching as high as No. 9 in the combined ITF junior world rankings in April 2009.

Australian Open: –
French Open: 3R (2009)
Wimbledon: 2R (2009)
US Open: 2R (2009)

Sandgren was a January midseason addition to the Tennessee Volunteers' 2010 tennis roster, joining older brother, Davey, who was a senior All-American on the team. Coached by Sam Winterbotham and Chris Woodruff, the younger Sandgren immediately strengthened the middle of the Vols' singles lineup, going 10–0 in Southeastern Conference play at the No. 4 position to help the team win the SEC regular-season and tournament titles. The team reached the NCAA team finals that year.

As a sophomore, Sandgren reached the semifinals of the NCAA Singles Championships, losing to teammate, roommate and doubles partner Rhyne Williams in three sets. He finished the season with a 37–6 record and his 10–1 record in conference helped the Vols to an SEC regular-season title. He finished his career with a 60–12 singles record (83.33 percent), the third-best career winning percentage in Tennessee history.

He was also a member of the USTA Summer Collegiate Team after his freshman and sophomore seasons.