Newcastle is a community in the municipality of Clarington in Durham Region, Ontario, Canada.

It has been named one of the best small towns in Ontario, by Comfort Life, a website for retirement living in Canada.

It remained a small community until the 1990s, when new residential development began and the population quickly swelled.

Newcastle is surrounded by farms raising cattle, pigs, apples, grain, and corn.

Most rural route and suburban mail is now handled by the Bowmanville Canada Post.