Mayu Watanabe (Watanabe Mayu, born March 26, 1994) is a Japanese singer, actress, and former member of the Japanese idol girl group AKB48 under Team B. In the group's general elections, she had consistently ranked among the group's top members. She has released five solo singles, many of which have peaked in the top ten in the Oricon charts. She left the group on the last day of 2017.

Watanabe auditioned for AKB48's 3rd generation and was placed in the newly formed Team B. Her first appearance on an AKB48 single title track was on "Bingo!". She performed in all of the singles except when the lineups were determined by rock-paper-scissors tournaments, she has appeared on all the A-sides for the group's singles since then.

In 2009, she placed fourth overall in the group's first general election to determine the line-up for the group's 13th single. She placed fifth overall the next year for the group's 17th single.

She appeared on the cover of the December 2010 issue of UP to boy magazine together with Airi Suzuki from Cute. That was the first gravure collaboration between Hello! Project and AKB48.

On May 13, 2011 she released her photo book, Mayuyu. She commented that the book "is filled with a lot of expressions that I haven’t shown until now, it’s a book I’m really pleased with!” Regarding her cover picture, she said, “Despite being embarrassed, I did my best on the front cover, so I want a lot of people to look at it!” In an episode of the group's variety show AKBingo!, then fellow AKB48 member Haruka Shimazaki revealed that Watanabe's nickname, Mayuyu, and her own, Paruru, were both coined by former teammate Rumi Yonezawa. For AKB48's general election in 2011, Watanabe placed fifth overall.

In 2012, Watanabe got her first lead role in the Japanese TV drama Saba Doru, where she played a 38-year-old high school teacher who is hated by her pupils, whilst having a hidden life as the highly popular idol Mayu Watanabe, based on her real-life self. On February 29, Watanabe released her debut solo single, "Synchro Tokimeki", which is also the opening theme for the drama.

Watanabe participated as a voice actress in the anime series AKB0048. In the anime, she plays a main character Chieri Sono, and is part of the AKB48 subgroup NO NAME, which sings the opening and ending themes for the series. The series features a supporting character, Mayu Watanabe Mark 3, which is modeled after her likeness, and is voiced by Yukari Tamura. She reprised her role as Chieri Sono for the series' second season which aired in 2013.

Watanabe ranked second overall at the 2012 AKB48 general elections with 72,574 votes. On August 24, during the group's reorganization announcement at the AKB48's Tokyo Dome concert, she was moved from Team B to Team A.[

On July 25, she released her second solo single, "Otona Jellybeans". which reached number three on the Oricon weekly chart. Her third solo single "Hikaru Monotachi" was released on November 21, 2012, and reached number one in the Oricon singles chart. The single was released in five versions, including one that has an illustration book. Her B-side "Sayonara no Hashi" was the theme song to the anime film Nerawareta Gakuen for which she voiced one of the lead characters. In July 2013, she released her fourth solo single. "Rappa Rensh?ch?". A contest was held to determine the cover artwork for one of its editions.

Meanwhile, in AKB48, she received her first center position on the group's 30th single "So Long!", which was released on February 20, 2013. On April 19, she released her second photobook Seifuku Zukan Saigo no Seifuku. In the AKB48 election for the members for their 32nd major label single, she placed third overall with 101,210 votes.

In 2014, Watanabe become a regular on the television show Utage!, and semi-regular on the TV show Renai Sosenkyo. In AKB48, she was transferred from Team A to Team B in the "Daisokaku Matsuri". She performed an hour-long solo live concert at AKB48's Natsu matsuri. In the elections to determine the member line-up for AKB48's 37th major label single, she placed first, with 159,854 votes. Thus, she took centre position for the song "Kokoro no Placard".

In 2015, Watanabe received her first leading role in a prime-time TV drama, Tatakau! Shoten Girl, broadcast by Fuji TV and Kansai TV. This drama aired from April 2015, at 10 pm. The theme song for this drama, "Deai no Tsuzuki", was sung by Watanabe, and was also released as her fifth solo single on June 10, 2015. She held solo live concerts to support the single on September 19. In 2015, a web poll conducted by My Navi Student declared her the second Cutest Idol from both the men's choices and women's choices lists, behind Kanna Hashimoto of the idol group Rev. from DVL.

On October 26, 2016, Watanabe released her third photobook "Shiranaiuchini".

On June 17, 2017, Watanabe announced at the 9th General Election she will graduate from the group. On October 31, Watanabe had her graduation concert. Later she had her last handshake on November 18, 2017. She performed at the AKB48 theatre for the last time on December 26, 2017. She song and performed on the stage of the "68th NHK Kouhaku Uta Gassen" on December 31, 2017, it was her last activity as a member of AKB48.