Thiells is a hamlet located in the town of Haverstraw in Rockland County, New York. It is located along Harriman State Park. The hamlet is located about 35 miles from New York City.

According to the United States Census Bureau, as of 2000 Thiells has a population of more than 4,500 residents. The hamlet has a total land area of 1.9 square miles. The hamlet is located at an elevation of over 270 feet above sea level.

The racial demographics of Thiells are 88.10% White, 3.89% African American, 0.23% Native American, 2.82% Asian, 3.47% from other races, and 1.49% from two or more races. Hispanic or Latino of any race are 12.65% of the population.

Thiells has more than 1,500 households, many of which are affluent. The median income for a household in the hamlet is $79,906, and the median income for a family is $86,872.

Thiells is home to the Philip J. Rotella Golf Course and North Rockland High School.