The Isotope is an American catamaran sailing dinghy that was designed by Frank Meldau as a one-design racer and first built in 1962.

The hulls have spooned raked stems, vertical transoms, transom-hung, kick-up rudders controlled by a tiller and retractable, self-tending centerboards.

[1][2][4] The boat has a draft of 2.50 ft (0.76 m) with the centerboards extended and 6 in (15 cm) with them retracted, allowing beaching or ground transportation on a trailer.

[1] For sailing the design may be equipped with options such as a mast limiter, roller furling jib and a trapeze.

[2] In a 1994 review Richard Sherwood wrote, "sister to the Cheshire, the Isotope is two feet longer and five Portsmouth numbers faster.