Dame Olivia Newton-John AC DBE (born 26 September 1948) is a British-Australian singer, songwriter, actress, entrepreneur and activist. She is a four-time Grammy Award winner whose chart career includes five US number ones and another ten Top Tens on Billboard's Hot 100. and two Billboard 200 number-one albums, If You Love Me, Let Me Know (1974) and Have You Never Been Mellow (1975). Eleven of her singles (including two platinum) and 14 of her albums (including two platinum and four 2× platinum) have been certified Gold by the Recording Industry Association of America (RIAA). She has sold an estimated 100 million records worldwide, making her one of the best-selling music artists of all time. In 1978, she starred in the musical film Grease, whose soundtrack remains one of the most successful in history. It features two major hit duets with co-star John Travolta: "You're the One That I Want" – which ranks as one of the best-selling singles of all time – and "Summer Nights". Her signature solo recordings include the Record of the Year Grammy winner "I Honestly Love You" (1974) and "Physical" (1981) – Billboard's top Hot 100 single of the 1980s – plus her cover of "If Not for You" (1971), "Let Me Be There" (1973), "If You Love Me (Let Me Know)" (1974), "Have You Never Been Mellow" (1975), "Sam" (1977), "Hopelessly Devoted to You" (also from Grease), "A Little More Love" (1978), "Heart Attack" (1982) and, from the 1980 film Xanadu, "Magic" and "Xanadu" (with Electric Light Orchestra). Newton-John has been a longtime activist for environmental and animal rights issues. She has been an advocate for health awareness, becoming involved with various charities, health products and fundraising efforts. Her business interests have included launching several product lines for Koala Blue and co-owning the Gaia Retreat & Spa in Australia.