Joseph Hardcastle

• Joseph Hardcastle (1752–1819), English merchant and a founder of The Missionary Society
• Joseph Hardcastle (politician), grandson of the above and British Liberal Party MP
• Joseph Alfred Hardcastle, FRAS, grandson of Joseph Hardcastle (politician) and Sir John Herschel appointed Director of Armagh Observatory just before his death
• Joseph Hardcastle (accountant), American Certified Public Accountant