Robert John "Mutt" Lange

In 2011, Lange purchased Coronet Peak Station located on the mountain and ski field of the same name in Queenstown, New Zealand. In 2014, he protected 53,000 hectares (130,000 acres) of his land as Queen Elizabeth II National Trust covenant; this is the largest private conservation covenant in New Zealand.

On 15 May 2008, a spokesman for his employer Mercury Nashville announced that Twain and Lange were separating, after Lange had an affair with Twain's then best friend and secretary, Marie-Anne Thiébaud, with whom he reportedly later began a relationship and moved to Switzerland with. Lange and Twain divorced in June 2010. On 1 January 2011, Twain married Frédéric Thiébaud, the former husband of Marie-Anne.

In the 2001 television film Hysteria – The Def Leppard Story, actor Anthony Michael Hall portrayed Lange.

After Hysteria, Lange bowed out of working with Def Leppard. In 1999, he returned to working with them in a more limited role, co-writing three tracks for their album Euphoria. One of those songs, "Promises", was a Number 1 hit on the mainstream rock charts for the band.

After hearing Shania Twain's music, he got in touch with her and they spent many hours on the phone. They finally met six months after the initial contact and were married on 28 December 1993. Lange is a teetotaler and, as a result, they had non-alcoholic champagne at their wedding. Lange had the song "(Everything I Do) I Do It for You" performed as a sign of his dedication to Twain. In August 2001, their son Eja (pronounced "Asia") was born.

In 1991, he produced Bryan Adams's Waking Up the Neighbours, including co-writing "(Everything I Do) I Do It for You", for the Kevin Costner film Robin Hood: Prince of Thieves which, with 16 consecutive weeks at the top, from 7 July to 26 October 1991, holds the record for the longest number of consecutive weeks at Number 1 in the UK singles chart. Lange produced the single "Make You" from the album Great Escape by Irish singer Tara Blaise which was released in May 2008.

He produced two more albums with AC/DC, including Back in Black (1980), which is, as of 2019, the second-best-selling album of all time. He also worked with rock group Foreigner with 4, and with Def Leppard on their hit albums, High 'n' Dry, Pyromania, Hysteria and Adrenalize co-writing most of the songs.

In 1978, Lange wrote and produced Ipswich Town's FA Cup final single "Ipswich Get That Goal", his connection with the club being due to their South Africa-born player Colin Viljoen. The song is derived from a previous recording "Give That Thang To Me" by Paul Jones (1977), with some parts rearranged and new lyrics.

Beginning production work in 1976, his first major hits came in October 1978 with the UK No. 1 single "Rat Trap" for The Boomtown Rats, followed in July 1979 with AC/DC's hard rock album Highway to Hell (#8 UK, No. 17 US). He produced a total of five albums for UK band City Boy from 1976 to 1979.

After his national service (1966–1967), Lange formed the band Sound Reason in 1969, together with James Borthwick, a South African TV, stage and film actor. In 1971, he started the group Hocus, recording one album and releasing five singles.

Lange met Stevie Vann when the two attended the same school in Northern Rhodesia in the early 1960s, and the two reconnected a few years later while attending Belfast High School in South Africa. They played together in a short-lived band named Hocus, and later married and emigrated to the United Kingdom in the 1970s. The marriage broke down in the 1970s. While still married, Lange started a five-year relationship with Oonagh O'Reilly, an Irish-born co-worker.

Robert John "Mutt" Lange (born 11 November 1948) is a South African record producer and songwriter, mainly known for his work in rock music as well as his previous marriage to Canadian singer Shania Twain, for whom he wrote and produced several songs. Her 1997 album Come On Over, which he produced, is the best-selling country music album, the best-selling studio album by a female act, the best-selling album of the 1990s, and the 9th best-selling album in the United States. He has also produced songs for, or otherwise worked with, artists such as AC/DC, Def Leppard, The Michael Stanley Band, The Boomtown Rats, Foreigner, Michael Bolton, The Cars, Bryan Adams, Huey Lewis and the News, Billy Ocean, Celine Dion, Britney Spears, The Corrs, Maroon 5, Lady Gaga, Now United, Nickelback, and Muse.