Younes El Aynaoui () (born September 12, 1971 in Rabat, Morocco) is a professional tennis player from Morocco.

In 1990, at the age of 18, El Aynaoui traveled to Bradenton, Florida, to spend a week at the Nick Bollettieri Tennis Academy, after which he decided to turn professional. He continued to hone his skills at the academy for the next two years where, in order to afford the fees, he drove the academy bus, cleaned the gym, strung rackets, tossed practice balls to campers, and helped to babysit younger players.

In 1993, he reached his first top-level grand prix singles final in Casablanca, where he lost to the Argentinian player Guillermo Perez-Roldan.

After finishing runner-up in three tour events in 1996, El Aynaoui suffered a broken right ankle. He had surgery on his ankle in November that year, but the injury continued to cause him problems. He missed seven months of the season in 1997 and had a second surgery in February 1998. He returned to the tour that summer ranked World Number 444, and enjoyed a run of strong results. He won five Challenger series tournaments and finished runner-up at one top-level event in Santiago. By the end of the year he had improved his ranking to World No. 49, and was named the ATP's Comeback Player of the Year.

In 1999, El Aynaoui won his first top-level singles title in Amsterdam.

In 2000, El Aynaoui reached the quarter-finals of the Australian Open where he lost to Yevgeny Kafelnikov.

El Aynaoui won his second top-level title in 2001 at Bucharest. He was also runner-up in Amsterdam that year, losing in the final to Alex Corretja in a five-set, 53-game match (6-3, 5-7, 7-6, 3-6, 6-4) which was the year's longest tour final. He was also runner-up in Lyon, defeated by Ivan Ljubičić in final.

El Aynaoui captured three tour titles in 2002 (Casablanca, Doha and Munich), and reached the quarter-finals of the US Open.

The most famous match of El Aynaoui's career came at the Australian Open in 2003. He qualified for the match by defeating World No. 1 Lleyton Hewitt in four sets in the fourth round, thus setting-up a quarter-final showdown with the up-and-coming American Andy Roddick (who would go on reach the World No. 1 ranking later that year). The five-set, five-hour match included the longest fifth-set in Grand Slam tennis history. Roddick eventually won the titanic battle 4-6, 7-6, 4-6, 6-4, 21-19. Both players saved match points against them before the marathon fifth-set finally concluded. El Aynaoui also reached the quarter-finals of the US Open that year, and finished the season ranked a career-high World No. 14.

El Aynaoui is an extremely popular figure in Morocco. He received a gold medal – the nation's highest sporting honor – from King Mohammed VI. In a 2003 poll by leading Moroccan newspaper L'Economiste, readers named El Aynaoui their favorite role model for society, ahead of the prime minister and athletics star Hicham El Guerrouj. The center court of the Royal Tennis Club in Marrakech is named after El Aynaoui.

After a three year hiatus due to injury, El Aynaoui made a comeback to the ATP tour in January 2007, and was awarded a Wildcard at the Qatar Open, Doha. He beat former Australian Open winner Thomas Johansson with two tie-breaks in the first round, only to be defeated 6-3 6-4 in the second round by the then World No.5, Ivan Ljubičić. However the match was closer than the scoreline suggests.

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