Katherine Sebov (born January 5, 1999) is a Canadian professional tennis player. She reached a career-high WTA singles ranking of No. 190, on 16 January 2023, and a career-high ITF junior ranking of No. 22, on 20 July 2015. Early life Sebov was born in Toronto and is of Ukrainian descent. Her coaches are Simon Bartram in Toronto and Robert Lansdorp in Los Angeles. Tennis career 2013–14 Sebov made her professional debut in November 2013 at a $50k event in Toronto, but was defeated in the qualifying second round in singles and in the first round in doubles. In July 2013, she had won her first junior singles title at the G4 in Vancouver. In July 2014 at Wimbledon, she qualified for her junior Grand Slam main-draw debut where she lost in the first round in singles and in the quarterfinals in the doubles. In September 2014, Sebov advanced to the third round in singles as a qualifier at the junior US Open and was defeated in the first round in doubles. 2015 In January, Sebov won her second singles junior title, this time at the G1 in Traralgon. A week later, she reached the second round in singles and the quarterfinals in doubles at the junior event of the Australian Open. In March, she qualified for the $25k main draw in Rancho Santa Fe, but fell in the first round to CiCi Bellis. Sebov made it to the second round in singles and to the first round in doubles at the junior French Open in May. In June at the junior competition of Wimbledon, she was eliminated in the first round in singles and in the second round in doubles. In July, she qualified for the main draw of the $50k event in Granby, defeating, respectively, compatriot Catherine Leduc (world No. 155), Julia Glushko, and fellow Canadian Petra Januskova. She was eliminated by Amandine Hesse (No. 224) in the opening round. At the US Open junior tournament, she fell in the first round in singles. 2016 At the Australian Open, Sebov advanced to the third round of the junior event in singles but was defeated in the first round in doubles. She decided to focus on the pro circuit for the rest of the season and did not play any other junior tournaments. In May, she reached back-to-back semifinals at $10ks in Antalya. In October, she qualified at the