Sabalenka was born on 5 May 1998 in Minsk, the capital of Belarus. Her father Sergey (d. 2019) was a hockey player. Aryna started playing tennis by chance. She said, “One day, my dad was just driving me somewhere in the car, and on the way he saw tennis courts. So he took me to the courts. I really liked it and enjoyed it and that’s how it was. That’s how it started.” She began training at the National Tennis Academy in Minsk when it opened in 2014.

Sabalenka began playing on the ITF Women’s Circuit in 2012, even before she competed on the ITF Junior Circuit. Her first five tournaments were in her hometown of Minsk and spread out over two years, but she did not win a main draw match in any of them. She won her first professional match at the very end of 2014 in Istanbul. The following season in October, she won her first two titles in back-to-back weeks in Antalya, both at the $10K level. Sabalenka also won a $25K title the last week of the year. This title put her into the top 300 of the WTA rankings for the first time at the start of 2016. That year, she made her Fed Cup debut in April, losing her only match. She also won her two biggest titles to date at the $50K level. The first in Tianjin put her into the top 200 in May and the second in Toyota in November helped her finish the year ranked at No. 137 in the world.

Sabalenka won her first ITF title in doubles at the lowest-level Grade 5 Alatan Tour Cup in Belarus in late 2013 with compatriot Vera Lapko as her partner. In 2014, she excelled at Grade 4 events. She reached her first singles final at the Estonian Junior Open in June and won her first singles title at the MTV Total Junior Cup in Finland in October. At the end of the season, Sabalenka defended her Alatan Tour Cup doubles title, this time with compatriot Nika Shytkouskaya, and also won the singles title. She only played in one tournament in 2015, the European Junior Championships. As a Grade B1 event, this was the highest level junior tournament she played in. She lost in the second round to top seed Markéta Vondroušová.

Sabalenka represented Belarus at the Junior Fed Cup in 2014, with the team finishing in 6th place. She then made her senior Fed Cup debut for Belarus in April 2016, losing a dead rubber doubles match against Russia. Nonetheless, the Belarusian team led by Victoria Azarenka and Aliaksandra Sasnovich won the tie to qualify for the top-tier World Group the following season for the first time in their history.

In 2015, the Belarusian Tennis Federation persuaded Sabalenka and her team to focus on playing low-level professional events instead of junior tournaments, even though she was still eligible to compete at the junior level at the time.

Sabalenka started the year ranked No. 73 in doubles. She began partnering with Elise Mertens in January, when the pair lost to top seeds Barbora Krejčíková and Kateřina Siniaková in the third round of the Australian Open. They had their breakthrough in March at the two Premier Mandatory tournaments. In only their second tournament together, Sabalenka and Mertens won the Indian Wells Open. They defeated three of the top five seeds in the event, including second seeds Tímea Babos and Kristina Mladenovic in the first round and top seeds Krejčíková and Siniaková in the final. The pair matched this success at their next event by winning the Miami Open to complete the Sunshine Double. They defeated three of the top six seeds, including third seeds Hsieh Su-Wei and Barbora Strýcová in the second round. They won the final against sixth seeds Samantha Stosur and Zhang Shuai. With these two titles, Sabalenka rose to No. 21 in the world. Sabalenka and Mertens became the fifth doubles partnership in history, and first since Martina Hingis and Sania Mirza in 2015, to complete the Sunshine Double in doubles.

After playing relatively few WTA events in 2017, Sabalenka utilized her higher ranking to play exclusively on the WTA Tour in 2018. She reached two quarterfinals to begin the year, but lost her opening round match at the Australian Open to top-ranked Australian and world No. 18 Ashleigh Barty. She then won her first matches at a Premier tournament with a third round appearance at the Indian Wells Open before the early-year hard court season came to a close, including a victory over No. 19 Svetlana Kuznetsova.

Although Sabalenka once again struggled at the Grand Slam tournaments, she ultimately finished the year with the same year-end ranking as in 2018 on the strength of three titles, all in China. She began the season by winning her third career WTA title at the Shenzhen Open, defeating Alison Riske in the final in a tight three-set match. Due to rain delays in the earlier rounds, she needed to play both the semifinal and the final on the last day of the tournament. However, she could not build on this success in the rest of the first half of the year. Sabalenka lost to 17-year-old Amanda Anisimova in straight sets at both the Australian Open and the French Open in the third and second rounds respectively. She had been considered the third-leading favourite for the title at the Australian Open. Nonetheless, she made her top 10 debut following the event. Sabalenka fared worse at Wimbledon, losing her opening match to No. 139 Magdaléna Rybáriková. In-between the Grand Slam tournaments, Sabalenka’s best result was a semifinal loss to No. 8 Kiki Bertens at the Premier-level St. Petersburg Ladies’ Trophy in February. She also made the fourth round at the Indian Wells Open. Her best result on clay was a semifinal at the Internationaux de Strasbourg in May.

Belarus was unable to repeat their 2017 Fed Cup success in 2018. Their quarterfinal tie was held in Minsk against Germany. Although Sabalenka won both of her singles rubbers, Sasnovich and Vera Lapko lost each of theirs to set up a decisive doubles rubber. Sabalenka and doubles specialist Lidziya Marozava were selected for the match, with Sabalenka playing on short rest directly after her last singles match. After taking the first set against Anna-Lena Grönefeld and Tatjana Maria, they ultimately lost the rubber and the tie.

Sabalenka had worked with Khalil Ibrahimov for two years up until early 2018. At this point, she began working with former Swedish professional tennis players Magnus Norman and Magnus Tideman. Dmitry Tursunov became her primary coach in time for the grass court season in 2018. Sabalenka briefly split with Tursunov after the 2019 US Open. Although they reunited later in the year, she made the split permanent at the end of the season. Sabalenka briefly worked with Dieter Kindlmann before switching coaches to her longtime hitting partner and compatriot Anton Dubrov.

In the 2019 Fed Cup, Belarus were drawn against Germany in the quarterfinals for the second consecutive year. After Sasnovich won the opening rubber against Maria, Sabalenka won both of her singles rubbers against Andrea Petkovic and Laura Siegemund to clinch the tie. They advanced to face Australia in the semifinals. Only two players from each team participated: Sabalenka and Azarenka for Belarus, and Ashleigh Barty and Samantha Stosur for Australia. Both Sabalenka and Azarenka defeated Stosur, but lost to Barty. In the decisive doubles rubber, Barty and Stosur won in three sets to eliminate Belarus.