Serena Williams made her professional debut at the Bell Challenge in Quebec in October 1995, when she was 14 years old. However, she was defeated by Annie Miller, who was 18 years old at the time, in the first round of qualifying. Serena won her first major title in 1997 at the Ameritech Cup in Chicago. She defeated No. 7 Mary Pierce and No. 4 Monica Seles, despite being ranked No. 304. Her victories over players in the top 10 were her first. In doing so, Serena became the lowest-ranked player in Open Era history to defeat two top-10 opponents in a single tournament. In the semifinals, she was defeated by No. 5 Lindsay Davenport.

Serena defeated Amélie Mauresmo in the Open Gaz de France final in Paris in 1999 to claim her first professional singles championship. Williams' career-defining competition may be regarded as the 1999 U.S. Open. She advanced to the semifinals by defeating three Grand Slam champions in a row: Kim Clijsters, Conchita Martnez, and Monica Seles. Serena Williams upset reigning champion Lindsay Davenport in the semi-finals. She won her first Grand Slam singles championship after defeating No. 1 Martina Hingis 6-3, 7-6 in the final. After Althea Gibson in 1958, she was the second African-American woman to achieve this feat by winning a Grand Slam singles match.

No. 3 Martina Hingis in the Miami Masters quarterfinals, No. 2 Venus in the semifinals, and No. 1 Jennifer Capriati in the championship match. She was the third player in the Open Era to do it in a single tournament, defeating the top three players. Serena was the third seed at the French Open. She won her second Grand Slam singles title after defeating the previous champion, Capriati, in the semifinals and her sister Venus in the championship match. After beating Venus in the Wimbledon singles final, Serena, ranked No. 2, went on to win the championship.

She also made history by being the first woman to win a Grand Slam singles title without dropping a set. Additionally, Serena became the first player to hold the No. 1 ranking in the world after winning at Wimbledon. After Althea Gibson and her sister, Venus Williams, Serena became the third African American woman to occupy that position. Serena Williams won the singles championship at the 2002 US Open after defeating Venus in the finals. She became the first woman since Martina Hingis in 1997 to win three Grand Slam singles championships in a calendar year. She also accomplished the "Surface Slam," which entails winning three Slam tournaments on three different surfaces in the same year, becoming just the third player in tennis history to do so.

One of the major accomplishments of Serena Williams is that she is only the second woman in history to hold four slams simultaneously twice. Serena won the 2003 Australian Open as a follow-up to her three grand slam victories in 2002. She defeated her sister Venus in the final to win the fourth straight Grand Slam. With her victory at the Australian Open, Serena became the sixth woman in the Open Era to complete a career Grand Slam, winning all four Grand Slam events (Australian Open, French Open, Wimbledon, and U.S. Open) thanks to her victory at the Australian Open.

Margaret Court, Billie Jean King, Chris Evert, Martina Navratilova, and Steffi Graf were the first five women to achieve this achievement. Serena joined Maureen Connolly Brinker, Court, Graf, and Navratilova as the sixth woman to capture all Grand Slam singles championships concurrently. Serena did it again in the 2014–15 season. After Rod Laver and Steffi Graf, she became the third player in tennis history to hold all four Grand Slam singles championships at the same time twice.

Serena Williams' career declined from 2004 to 2007, following a good start due to injuries and other factors. Serena had missed five of the previous 13 major championship matches before she entered the 2007 Australian Open, and she was ranked outside of the top 100. Williams was under a lot of pressure to do well. She was two points away from losing her match against Nadia Petrova in the third round of the competition. She, on the other hand, rallied back to win in three sets. Serena faced up against Maria Sharapova in the tournament's final, with the latter being the press and pundits' favorite to win.

But Serena destroyed Sharapova in the championship match, winning 6–1, 6–2 with just three games lost. Her last effort was dubbed "one of the finest performances of her career" and "probably the most powerful exhibition ever witnessed in women's tennis" by the press. Serena Williams became the first unseeded player to win the Australian Open since Christine O'Neil did so in 1978.

Serena and her sister Venus won the gold medal in the doubles competition at the Sydney Summer Olympics in 2000. Venus and Serena once again won the doubles event at the Beijing Olympics in 2008 after defeating Anabel Medina Garrigues and Virginia Ruano Pascual. The team replicated the feat at the London Olympics in 2012, taking home their third doubles gold medal. Venus had already won the gold medal in the Olympic singles competition, but Serena had not. She won the singles gold medal at the 2012 Olympics by defeating her longtime adversary Maria Sharapova in the final 6-0, 6-1. This is obviously one of the major accomplishments of Serena Williams.

Thus, Serena has four Olympic gold medals to her name, tying her sister Venus for the most in history. Additionally, by winning the singles gold medal, she achieved the career Golden Slam, which entails winning the Olympic gold as well as all four Grand Slams. Only two women—Serena Williams and Steffi Graf—have ever achieved a lifetime Golden Slam. The William sisters were unable to add to their collection of gold medals at the 2016 Summer Olympics in Rio de Janeiro. Additionally, they lost their doubles match after a 15-match winning run.

The sixth major accomplishment of Serena is that she has won a record 23 Grand Slam singles titles. Serena Williams now has 18 Grand Slam singles titles after winning the 2014 US Open. This equaled her for the second highest women's singles total in the Open Era, after Chris Evert and Martina Navratilova. Serena won her 22nd Grand Slam at Wimbledon in 2016 by defeating Angelique Kerber. As a result, she tied Steffi Graf's Open Era record for the most singles Grand Slam victories. Serena Williams defeated her sister to win the 2017 Australian Open for the seventh time. Her most recent triumph at a Grand Slam is this one. Additionally, this was her 23rd overall Grand-Slam singles victory.

The fact that Serena was at least eight weeks pregnant at the time of her victory was astounding. Serena Williams has won the most Grand Slam singles titles in the Open Era with her 23 victories. She also holds the second-highest record of all time, trailing only Margaret Court (24).

On July 8, 2002, Serena Williams attained the top spot for the first time. Serena was the top-ranked player in 2014 at the start and conclusion of the year. She subsequently made history by being the first player to do it since Steffi Graf in 1996. For the second year in a row, Williams remained at the top of the rankings for the entire 2015 season. Serena now has the second-longest streak in WTA history, trailing only Steffi Graf's 186 matches, after surpassing Navratilova's previous record of 156 in February 2016.

Williams's 186th straight week at No. 1 on September 5, 2016, matched Graf's record for the longest streak in WTA history. After that, though, she dropped to No. 1, breaking her streak with a tied record. Between 2002 and 2017, Serena achieved the top singles ranking eight times. She has been No. 1 for 319 weeks in total, second only to Graf and Navratilova among women in the Open Era. While Navratilova has held the rank for 332 weeks, Graf has held it for 377 weeks.

Winning 14 Grand Slam women's doubles matches with Venus Williams is Serena Williams' sixth significant accomplishment. Along with her sister Venus, Serena owns several doubles records in addition to being a dominant singles winner. Since 1997, Venus and Serena have occasionally played doubles together. At the 1999 French Open, they won a Grand Slam title for the first time, marking their first significant achievement. Serena was 17 at the time, and Venus was 18 at the time. The team achieved the Career Doubles Grand Slam by winning the 2001 Australian Open. They also achieved a career doubles grand slam because they had already won the gold medal at the 2000 Olympics. Venus and Serena have won 14 Grand Slam doubles championships overall.

This is the third-most titles in women's doubles, after Navratilova and Pam Shriver's record-breaking 20 titles and Natasha Zvereva's 18 titles (14 with Gigi Fernández). At major slams, Venus and Serena have a 125-14 win-loss record. They have also never lost a Grand Slam championship.

One of the major accomplishments of Serena Williams is that she has the third-most grand slam titles overall. Serena Williams has taken home 39 Grand Slam victories in total, including 23 in singles, 14 in women's doubles, and two in mixed doubles. Serena is third on the list, tied with Billie Jean King, who also holds 39 Grand Slam trophies, and Margaret Court, who has 64 titles overall. Martina Navratilova is second with 59. Serena has won six U.S. Open singles championships, which puts her in a tie with Chris Evert for the most in the Open Era. Her seven singles championships at the Australian Open are the most in the Open Era. Serena now has the hard-court Grand Slam singles record with 13 victories.

Serena has won seven women's singles Wimbledon championships. Navratilova now holds the record with 9. She has three singles victories in the French Open. Chris Evert has won the most championships, with seven. With 351 victories, Serena also holds the record for the most major tournament victories in women's singles matches. Venus and Serena have won 14 Grand Slam championships together in doubles, including six Wimbledon Championships, four Australian Opens, two U.S. Opens, and two French Opens. Only Serena Williams has ever won the career Grand Slam in both singles and doubles tennis.

Serena Williams has earned a lot of prestigious prizes as a result of her astounding accomplishments. She received the WTA (Women's Tennis Association) Newcomer of the Year award in 1998 and the WTA Most Improved Player award the following year. Like Steffi Graf, she has won the WTA Player of the Year title seven times. Serena Williams has won the ESPY Award for Best Female Tennis Player ten times and the ESPY Award for Best Female Athlete twice, in 2003 and 2013. She shared the NAACP Image Award - President's Award in 2003 with her sister Venus.

In 2003, 2010, 2016, and 2018, she won the Laureus World Sports Award for Sportswoman of the Year. Additionally, in 2002 and 2009, she received the Associated Press Female Athlete of the Year award. Serena received the Sportsperson of the Year award from Sports Illustrated in 2015. Serena Williams was the highest-paid female athlete in 2016, earning about $29 million. She was the lone female athlete on Forbes' list of the top 100 earners in sports in 2017. She came in at number 63 on Forbes' list of the highest-paid athletes in the world in 2019.