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Specifications Under Current Rules
Number of Crew	3
LOA	5200 mm 17 ft
LWL
Beam	1800 mm 6 ft
Draft	1400 mm 4 ft 6in
Hull weight (with fittings)	334 kg 515 lb
Main Area and Jib Area	17.1 m² 191 ft²
Spinnaker Sail Area	20.4 m² 220 ft²

A Thistle sailing downwind.

The Thistle is a high performance racing dinghy, also used for day sailing, popular in the United States. The Thistle was designed by Gordon K. (Sandy) Douglass who later designed the Highlander and Flying Scot. (These names commemorate Douglass’s Scots heritage.) Starting in 1945, 4000 boats have now been built. Their construction originally used molded plywood. The builders started using Glass-reinforced polyester or "fiberglass" in the late 1950s. The current hull configuration uses a glass-reinforced polyester molded boat with wooden rails, center board trunk, thwart, fore grating, and aft grating. The spars were once made from spruce, but are now of entirely extruded aluminum construction.

The Thistle Class Association,[1] with fleets across the country, holds local, regional, and national regattas throughout the year. All Thistles are built to the same lines by authorized builders. Class rules limit innovations in rigging, restrict sail purchases, and prohibit electronic navigation gear. Old and new boats are evenly matched, with the owner of Thistle number 1 winning the national championship in 1990. Newer fiberglass hulls tend to "soften" over a period of 20 years, depending on use. "Softer" boats are still fast, but not competitive at the very highest level.

Thistle hulls are relatively light for their size; they have no decking or spray protection, which saves weight. The sail plan is large for a boat of this size, consisting of a marconi rig with a main, jib, and symmetrical spinnaker. The sail plan is larger for the boat’s weight than in many other dinghies, which makes Thistles perform well in light wind. Their hulls have wide flat bottoms, allowing the boats to plane in winds of 15 to 20 knots.

Thistles are generally raced with a three person crew. A skipper, a middle, and a forward person. The optimal total crew weight is generally 450 lb to 480 lb (US) depending on wind. The crew weight, however, is generally not the deciding factor in determining the outcome of the races. In all but the strongest winds, an experienced two person crew can manage the boat. Hiking straps are permitted for either droop or straight leg hiking, but a trapeze is not. The class is generally family friendly, though experienced sailors will still be challenged at the higher levels of competition.

The Thistle is used as the baseline for the U.S. version of the Portsmouth yardstick system for handicapping small boats in mixed-class fleets.

• Thistle Class Association web site