Helen Newington Wills (October 6, 1905 – January 1, 1998), also known by her married names Helen Wills Moody and Helen Wills Roark, was an American tennis player. She won 31 Grand Slam tournament titles (singles, doubles, and mixed doubles) during her career, including 19 singles titles.

Wills was the first American woman athlete to become a global celebrity, making friends with royalty and film stars despite her preference for staying out of the limelight. She was admired for her graceful physique and for her fluid motion. She was part of a new tennis fashion, playing in knee-length pleated skirts rather than the longer ones of her predecessors, and was known for wearing her hallmark white visor. Unusually, she practiced against men to hone her craft, and she played a relentless predominantly baseline game, wearing down her female opponents with power and accuracy. In February 1926 she played a high-profile and widely publicized match against Suzanne Lenglen which was called the Match of the Century.

Wills had a 180-match win streak from 1927 until 1933. In 1933, she beat the eighth-ranked US male player in an exhibition match. Her record of eight wins at Wimbledon was not surpassed until 1990 when Martina Navratilova won her ninth. She was said to be "arguably the most dominant tennis player of the 20th century", and has been called by some (including Jack Kramer, Harry Hopman, Mercer Beasley, Don Budge, and AP News) the greatest female player in history.

She was born as Helen Newington Wills on October 6, 1905, in Centerville, Alameda County, California (now Fremont), near San Francisco. She was the only child of Clarence A. Wills, a physician and surgeon at Alameda County Infirmary and Catherine Anderson, who had graduated with a B.S. degree in Social Science at the University of California at Berkeley. Her parents had married on July 1, 1904, in Yolo County, California.

She was tutored by her mother at home until she was eight years old. After her father enlisted in the military in December 1917 and was posted in France with the American Expeditionary Forces her mother enrolled her at Bishop Hopkins Hall in Burlington, Vermont. When World War I ended the family moved back to Northern California, to Berkeley, where they took up residence near Live Oak Park. Wills enrolled as a ninth-grader at the Anna Head School, a private day and boarding school, where she graduated in 1923 at the top of her class. Her father's family grew wheat and kept a ranch near Antioch, and she occasionally practiced her tennis game nearby at the Byron Hot Springs resort. Wills attended the University of California, Berkeley, as both her parents had done, on an academic scholarship, and graduated in 1925 as a member of Phi Beta Kappa honor society.

When she was eight years old, her father bought her a tennis racket and they practiced on the dirt courts next to the Alameda County Hospital as well as at Live Oak Park. Wills' interest in tennis was kindled after watching exhibition matches by famous Californian players including May Sutton, Bill Johnston and her particular favorite, Maurice McLoughlin. In August 1919, she joined the Berkeley Tennis Club as a junior member on the advice of tennis coach William "Pop" Fuller who was a friend of her father. In the spring of 1920, she practiced for a few weeks with Hazel Hotchkiss Wightman, four-time winner of the U.S. Championships singles title, on strokes, footwork and tactics.

In September 1919, at the age of 13, she entered her first tournament, the California State Championships, held at her own Berkeley Tennis Club. After a bye in the first round she lost in two close sets to Marjorie Wale. Reporting on the tournament the San Francisco Examiner commented that "she will bear watching in the future". By the end of 1919 she was the 7th ranked junior player in California. In 1920 she competed in four tournaments in Northern California (Sacramento, Berkeley and San Francisco) and at the end of 1920 she was the 9th ranked singles player in California. In July 1921 she traveled to the East Coast for the first time where she played in four warm-up tournaments on grass in preparation for the U.S. Girls National Championships in Forest Hills. The trip was sponsored by the California Tennis Association. In September 1921, Wills won the singles and doubles titles at the California State Championships, defeating Helen Baker in the final in three sets. At the end of 1921 Wills was ranked No. 14 in the national singles, No. 2 in the Californian ranking, behind Helen Baker and No. 1 in the national juniors.

In May 1922 she won the singles title at the Pacific Coast Championships, beating Ream Leachman in the final. During Wills's run of East Coast grass court tournaments in the run up to the U.S. Championships she lost four times to Leslie Bancroft. At the 1922 U.S. Championships she participated for the first time in the women's singles event and reached the final, losing just one set to Marion Zinderstein Jessup in the quarterfinal. The New York Times described the final between 16-year old Wills against 38-year old six-time champion Molla Mallory as the "battle of youth against experience". Mallory won the final in two sets to gain her seventh title. Wills won her first Grand Slam title in the doubles event, partnering Zinderstein Jessup, after a three-sets victory in the final against Mallory and Edith Sigourney. Partnering Howard Kinsey she was runner-up in the mixed doubles event to Mary Browne and Bill Tilden. She also took part in the girls' singles championship and successfully defended her 1921 title. At the end of the year she was the No. 3 ranked singles player nationally and the top-ranked player in California.