Sean Stuart Cairncross (born July 12, 1974) was the chief executive officer of the Millennium Challenge Corporation from 2019 to 2020, and a former senior adviser to U.S. President Donald Trump.

[2][3][4] Recently, he has served as the chief operating officer for the Republican National Committee.

He was nominated to be the National Cyber Director on February 11, 2025.

[5] If confirmed, he would succeed Harry Coker, the previous National Cyber Director.