2016: Wimbledon semifinal
Williams began 2016 by playing at the World Tennis Thailand Championship – an exhibition event in Thailand – where she lost to Sara Errani and Angelique Kerber. She then entered the Auckland Open, where she was the No. 1 seed and defending champion, and lost in the first round to 18-year-old Daria Kasatkina. (This was also Williams's first tournament since the 2011 Australian Open as a top-10 player.) At the Australian Open, Williams, seeded 8th, lost to Johanna Konta in the first round. Afterwards, she helped the USA Fed Cup Team to a 4–0 victory over Poland, winning both of her singles matches. Williams's next tournament was at the Taiwan Open, where she was the No. 1 seed. She defeated Misaki Doi in the final, earning her 49th career title.
Williams returned to Indian Wells for the first time in 15 years after boycotting the tournament in 2001, but lost in the second round to Kurumi Nara. The following week, she was knocked out in the second round of the Miami Open by qualifier Elena Vesnina. Both results marked her worst exits at Indian Wells and Miami in her 23-year career. She began the clay-court season with a win over Alison Riske at the Charleston Open, before losing to Yulia Putintseva in the third round in three tight sets. Williams was scheduled to begin her clay-court season at the Madrid Open but withdrew due to a hamstring injury. The following week, she lost in the second round in Rome. Seeded ninth at the French Open, Williams won her first two rounds in straight sets to set up a third-round clash with Alizé Cornet, whom she defeated in three sets to reach the fourth round for the first time since 2010. She recorded the 200th loss of her career against 8th-seeded Timea Bacsinszky, who won in straight sets. However, her result pushed her back into the top 10 for the first time since her loss at the Australian Open. She also won her first Grand Slam doubles match with sister Serena Williams since the 2014 US Open.
At the Wimbledon Championships, Williams reached the third round of the championships where she overcame the 29th seed, Daria Kasatkina, in a 2-hour, 42-minute marathon. She defeated 12th seed Carla Suárez Navarro in the fourth round, and now leads 4–3 in their head-to-head meetings. Williams advanced to the quarterfinals for the first time in six years, where she defeated Yaroslava Shvedova. In her first major semifinal since the 2010 US Open and her first Wimbledon semifinal since 2009, she lost to fourth seed Angelique Kerber in straight sets. In the doubles tournament, Venus and Serena Williams advanced to their first major final since 2012. They then won their 14th major title together and sixth at Wimbledon.
Williams began her US Open Series at the Stanford Classic, where she was the No. 1 seed. She defeated Magda Linette in the second round and compatriots Catherine Bellis and Alison Riske in the quarterfinals and semifinals, respectively, to reach her eighth final in Stanford. She lost to Johanna Konta, in three sets. By virtue of her result, Williams ascended to No. 6 in the rankings, her highest position since being diagnosed with Sjögren's syndrome in 2011. Williams then entered the Rogers Cup. Having received a bye in the first round, Williams won her second-round match against Barbora Strýcová, in straight sets. She fell to Madison Keys in the third round in three sets.
Williams failed to medal in her singles and doubles events at the 2016 Rio Summer Olympics, falling in the first round in both events, marking her worst exits of her Olympic career. She entered the mixed doubles event with Rajeev Ram, defeating the Netherlands in the first round after saving match point. The pair then defeated Italy in the quarterfinals and India in the semifinals to set up a clash with the United States team of Bethanie Mattek-Sands and Jack Sock in the gold medal match. The duo lost to Mattek-Sands and Sock. By winning a silver medal, Williams became the only female player (besides Kathleen McKane Godfree) to win a medal in all three events (singles, doubles and mixed); her five medals mean she now shares the record for most Olympic medals won in tennis with Godfree.
At the 2016 US Open, Williams broke the record for the most major appearances, surpassing Amy Frazier's record of 71. This is also the first time that she's been seeded in the top ten at all four Grand Slam tournaments this year, having last achieved this in 2010. She won her first three-round matches respectively against Kateryna Kozlova, Julia Görges and the 26th seed Laura Siegemund. She lost in the fourth round to 10th seed Karolína Plíšková after failing to convert match point.
In September 2016, in response to WADA database leak, Williams confirmed the usage of banned substances classified by WADA as Therapeutic Use Exemptions (TUEs), stating: "The applications for TUEs under the Tennis Anti-Doping program require a strict process for approval which I have adhered to when serious medical conditions have occurred".
Williams failed to defend her title in Wuhan, falling in the third round to ninth seed Svetlana Kuznetsova. This pushed her outside of the top ten for a second time this year. The following week she was bundled out of the China Open in the first round by No. 223-ranked Peng Shuai. Williams qualified for the WTA Elite Trophy, where she was the defending champion, however she decided not to participate. She finished the year ranked No. 17.
