The Catskill Mountains, also known as the Catskills, are a physiographic province of the larger Appalachian Mountains, located in southeastern New York. As a cultural and geographic region, the Catskills are generally defined as those areas close to or within the borders of the Catskill Park, a 700,000-acre (2,800 km²) forest preserve protected from many forms of development under New York state law.

Geologically, the Catskills are a mature dissected plateau, a flat region subsequently uplifted and eroded into sharp relief by watercourses. The Catskills form the northeastern end of the Allegheny Plateau (also known as the Appalachian Plateau).

The Catskills were named by early Dutch settlers. They are well known in American society as the setting for films and works of art, including many 19th-century Hudson River School paintings, as well as for being a favored destination for vacationers from New York City in the mid-20th century. The region's many large resorts gave many young stand-up comedians an opportunity to hone their craft. Since the late 19th century, the Catskills have been a haven for artists, musicians and writers, especially in and around the towns of Woodstock and Phoenicia.