James Slack CBE is a British political advisor and journalist who served as Downing Street Director of Communications for Prime Minister Boris Johnson between January and March 2021.

Previously home affairs editor of the Daily Mail, he was appointed political editor of the newspaper in October 2015 in succession to James Chapman, who had been appointed as spokesman for George Osborne, then Chancellor of the Exchequer.

At the Daily Mail, as home affairs editor, Slack was involved in the campaign to stop Gary McKinnon, who has Asperger syndrome, from being extradited to the United States to face charges relating to computer hacking.

Slack wrote the controversial "Enemies of the People" front-page article on 4 November 2016 which criticised senior judges in England's High Court of Justice who had made a decision the Daily Mail did not agree with.

At the end of January 2017 it appeared that Slack was to be appointed as the Prime Minister's Official Spokesperson, which was confirmed on 10 February 2017. He remained in the post after Boris Johnson took over the government on 24 July 2019.

Slack was appointed a Commander of the Order of the British Empire in Theresa May's resignation honours list for public service.

Following the announcement that the then-Downing Street Director of Communications, Lee Cain, had resigned from government and would leave his post at the end of December 2020 it was confirmed that Slack would assume this position in the new year.

In March 2021, it was announced that he was leaving Downing Street to join The Sun as deputy editor in succession to Keith Poole. He was replaced as Director of Communications by Jack Doyle, a former Daily Mail associate editor for politics.