She has been ranked world No. 1 in singles twice between 2017 and 2019, for a total of 64 weeks, which ranks eleventh in the history of the Women's Tennis Association (WTA) rankings. Halep was the year-end No. 1 in 2017 and 2018. From 2014 through 2021, she was ranked in the top 10 for 373 consecutive weeks, the eighth-longest streak in WTA history. During this seven-year span, she finished each year ranked no lower than No. 4. She has won 23 WTA singles titles and has finished runner-up 18 times. Halep has won two Grand Slam singles titles: the 2018 French Open and the 2019 Wimbledon Championships.
Halep first broke into the world's top 50 at the end of 2011, reached the top 20 in August 2013, and then the top 10 in January 2014. She won her first six WTA titles in the same calendar year in 2013, and was the first to do so since Steffi Graf in 1986. This led to her being named the WTA Most Improved Player at the end of the year. Halep reached three Grand Slam finals at the 2014 French Open, the 2017 French Open, and the 2018 Australian Open before winning her first Grand Slam singles title at the 2018 French Open against Sloane Stephens. A former junior champion there, she became just the sixth player to win both the girls' singles and women's singles titles at the French Open. Halep also finished runner-up at the 2014 WTA Finals to Serena Williams despite inflicting the worst loss of Williams' career at that point in the round robin stage. She did not defeat Williams a second time until the final of the 2019 Wimbledon Championships.
Halep was the WTA Most Popular Player of the Year for two consecutive years in 2014 and 2015, as well as the WTA Fan Favorite Singles Player of the Year for three consecutive years in 2017, 2018, and 2019. She is a recipient of the Patriarchal Cross of Romania and the Order of the Star of Romania, and was named an honorary citizen of Bucharest. She is the third Romanian to be in the top 10 of the WTA rankings after Virginia Ruzici and Irina Spîrlea, and the second Romanian woman to win a Grand Slam singles title after Ruzici. She is also the first Romanian woman to be ranked No. 1 and the first Romanian player to win a Wimbledon singles title. Halep is regarded as one of the best returners on the WTA Tour, while also building her game around being aggressive and being able to hit winners from defensive positions.
