Yoko Ono (Japanese: 小野洋子, romanized: Ono Yōko, usually spelled in katakana オノ・ヨーコ; born February 18, 1933) is a Japanese multimedia artist, singer, songwriter, and peace activist. Her work also encompasses performance art and filmmaking.

Ono grew up in Tokyo and moved to New York City in 1952 to join her family. She became involved with New York City's downtown artists scene in the early 1960s, which included the Fluxus group, and became well known in 1969 when she married English musician John Lennon of the Beatles, with whom she would subsequently record as a duo in the Plastic Ono Band. The couple used their honeymoon as a stage for public protests against the Vietnam War. She and Lennon remained married until he was murdered in front of the couple's apartment building, the Dakota, on December 8, 1980. Together they had one son, Sean, who later also became a musician.

Ono began a career in popular music in 1969, forming the Plastic Ono Band with Lennon and producing a number of avant-garde music albums in the 1970s. She achieved commercial and critical success in 1980 with the chart-topping album Double Fantasy, a collaboration with Lennon that was released three weeks before his murder, winning the Grammy Award for Album of the Year. To date, she has had twelve number one singles on the US Dance charts, and in 2016 was named the 11th most successful dance club artist of all time by Billboard magazine. Many musicians have paid tribute to Ono as an artist in her own right and as a muse and icon, including Elvis Costello, the B-52's, Sonic Youth and Meredith Monk.

As Lennon's widow, Ono works to preserve his legacy. She funded the Strawberry Fields memorial in Manhattan's Central Park, the Imagine Peace Tower in Iceland, and the John Lennon Museum in Saitama, Japan (which closed in 2010). She has made significant philanthropic contributions to the arts, peace, disaster relief in Japan and the Philippines, and other such causes. In 2002, she inaugurated a biennial $50,000 LennonOno Grant for Peace. In 2012, she received the Dr. Rainer Hildebrandt Human Rights Award and co-founded the group Artists Against Fracking.