James Arthur Ernst (born November 19, 1942) is a politician in Manitoba, Canada. He was a municipal councillor in Winnipeg from 1973 to 1986 and a member of the Legislative Assembly of Manitoba from 1986 to 1997. From 1988 to 1997, Ernst was a Cabinet minister in the government of Premier Gary Filmon.
The son of Frank Luther Ernst and Stella Sarah Bryson, he was born in Winnipeg and was educated at St. Paul's College (affiliated with the University of Manitoba). He worked as a real estate and insurance broker before entering public life. Ernst was elected as a councillor in the amalgamated City of Winnipeg in 1973, and served as the city's deputy mayor from 1981 to 1986. During his time in municipal politics, Ernst was associated with the Independent Citizens' Election Committee, an unofficial alliance of right-wing business interests in the city.
In 1967, he married Dorothy Lynn Blom. The seat had been vacated by former premier Sterling Lyon's retirement from electoral politics. The governing New Democratic Party (NDP) was narrowly re-elected, and Ernst joined 25 other Conservatives in opposition.
In March 1988, disgruntled NDP backbencher Jim Walding brought down the government. The resulting election took place at a time when the Manitoba Liberal Party was making inroads into both PC and NDP areas of support; Ernst was only narrowly re-elected, defeating Liberal candidate Shari Nelson by fewer than 1,000 votes.