Stefani Joanne Angelina Germanotta (born March 28, 1986), known professionally as Lady Gaga, is an American singer, songwriter and actress. Known for her image reinventions and versatility across the entertainment industry, she is an influential figure in popular music.

After signing with Interscope Records in 2007, Gaga achieved global recognition with her debut studio album, The Fame (2008), and its reissue The Fame Monster (2009). The project scored a string of successful singles, including "Just Dance", "Poker Face", "Bad Romance", "Telephone", and "Alejandro". Her second full-length album, Born This Way (2011), explored electronic rock and techno-pop and sold more than one million copies first week. Its title track became the fastest-selling song on the iTunes Store, with over one million downloads in less than a week. Following her electronic dance music-influenced third album, Artpop (2013), she pursued jazz on the album Cheek to Cheek (2014) with Tony Bennett, and delved into soft rock on the album Joanne (2016).

Gaga ventured into acting, winning awards for her leading roles in the miniseries American Horror Story: Hotel (2015–2016) and the musical film A Star Is Born (2018). Her contributions to the latter's soundtrack, which spawned the chart-topping single "Shallow", made her the first woman to win an Academy Award, BAFTA Award, Golden Globe Award, and Grammy Award in one year. Gaga returned to dance-pop with her sixth studio album, Chromatica (2020), which yielded the number-one single "Rain on Me", and released her second and final collaborative album with Bennett, Love for Sale (2021). She followed this with starring roles in the films House of Gucci (2021) and Joker: Folie à Deux (2024), and the Billboard Global 200 number-one single "Die with a Smile" (2024).

Having sold an estimated 170 million records, Gaga is one of the world's best selling music artists and the only female artist to achieve four singles each selling at least 10 million copies globally. Her five succeeding studio albums all debuted atop the US Billboard 200. Her other accolades include 13 Grammy Awards, two Golden Globe Awards, 18 MTV Video Music Awards, and awards from the Songwriters Hall of Fame and the Council of Fashion Designers of America. She has been recognized as Billboard's Artist of the Year (2010) and Woman of the Year (2015), and placed fifth on their Greatest Pop Stars of the 21st Century list (2024). Gaga has also been included in several Forbes power rankings and ranked fourth on VH1's Greatest Women in Music (2012). Time named her one of the 100 most influential people in the world in 2010 and 2019 and placed her on their All-Time 100 Fashion Icons list. Gaga's philanthropy and activism focus on mental health awareness and LGBT rights. She has her own non-profit organization, the Born This Way Foundation, which supports the wellness of young people. Her business ventures include vegan cosmetics brand Haus Labs, launched in 2019.