Authors born in 1940
- J. M. G. Le Clezio Writer, 1940
- Jack Nicklaus Golfer, 1940
- Jack Prelutsky Writer, 1940
- James Brady Public Servant, 1940
- James Brolin Actor, 1940
- James Burrows Television Director, 1940
- James Caan Actor, 1940
- James Cromwell Actor, 1940
- James L. Brooks Director, 1940
- Jeffrey Archer Novelist, 1940
- Jerry Gillies Author, 1940
- Jerry Heller Businessman, 1940
- Jerry Speyer Real Estate Developer, 1940
- Jill St. John Actress, 1940
- Jim Bakker Televangelist, 1940
- Jim Clyburn Politician, 1940
- Jimmy Greaves Football Player, 1940
- Joachim Frank Physician, 1940
- Joe Gibbs American Football Player, 1940
- Joe Torre Baseball Manager, 1940
- John Clute Author, 1940
- John Cornwell Journalist, 1940
- John Hagee Pastor, 1940
- John Hurt Actor, 1940
- John Lennon Singer, 1940
- John Lewis Politician, 1940
- John Mahoney Actor, 1940
- John Vinocur Columnist, 1940
- John Warnock Computer Scientist, 1940
- Johnny Giles Football Player, 1940
- Joseph Brodsky Poet, 1940
- Judith Moore Author, 1940
- K.P. Fabian Diplomat, 1940
- Karolyn Grimes Actress, 1940
- Katerina Gogou Poet, 1940
- Katharine Ross Actress, 1940
- Kazuo Chiba Teacher, 1940
- Keith Rowe Guitarist, 1940
- Kenneth Clarke Politician, 1940
- Kerry Stokes Businessman, 1940