Robin Montgomery

In August 2019, Montgomery competed in the girls' singles at the US Open where she reached the third round. In September, she represented the U.S. in the final of the Junior Fed Cup, teaming with Connie Ma to win the doubles match against the Czech Republic and secure victory for the US team. In December, she won the "18 and under" title in the 2019 Orange Bowl.

Montgomery reached the quarterfinals of the 2020 Australian Open girls' singles tournament in January, and in March, she won her first ITF tournament, a $25k event in Las Vegas. As of August 2020^[update], she was the No. 5 in the junior world rankings.

Following the break in the season caused by the COVID-19 pandemic, Montgomery took part in the Western & Southern Open as a wildcard entrant in the qualifying competition, losing in the first round to Sorana Cîrstea. The following week, she received a wildcard into the main draw of the 2020 US Open — her first Grand Slam appearance. She lost in the first round to Yulia Putintseva.

She made her WTA 1000 debut in the main draw of the Miami Open as a wildcard entrant.

At the US Open, Montgomery defeated Kristina Dmitruk in straight sets in the girls' singles final to win her first major singles title. She followed this victory a few hours later with her first major doubles title. She and partner Ashlyn Krueger defeated fellow American duo, Reese Brantmeier and Elvina Kalieva, in three sets. Montgomery became the first girl to achieve the feat of winning both titles at the US Open since Michaëlla Krajicek in 2004, and was the first American to take the girls' singles title since Amanda Anisimova in 2017.

She qualified for the inaugural 2023 ATX Open in Austin, Texas but lost in the first round.

She received a wildcard for the qualifying draw of the Indian Wells Open and for the main draw of the Miami Open, where she reached the second round, defeating Ana Bogdan for her first WTA 1000-level win.

In 2024, she qualified for the main draw in Indian Wells, having received a wildcard for the qualifying competition. She also received a wildcard for the qualifying competition in Miami. At the Madrid Open, also as a main draw wildcard, she reached the third round, losing to defending champion Aryna Sabalenka.

At the beginning of the grass-court season, she qualified for the Rosmalen Open and then reached her first tour-level quarterfinal defeating Jule Niemeier. She also qualified for the 2024 Wimbledon Championships.

At the beginning of the American summer swing, she reached her first WTA 500 quarterfinal at the Washington Open as a wildcard entrant, after defeating Shelby Rogers and receiving a walkover from fourth seed Ons Jabeur. She qualified for the main draw at the Cincinnati Open, having received a wildcard for the qualifying competition.

At Indian Wells where she received a wildcard, she defeated again Jule Niemeier in the first round, recording her first tournament win. Following her first-round match win at the Charleston Open over Viktoriya Tomova, Montgomery reached the top 100 on 7 April 2025.