The Thistle is a high performance one-design 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. Starting in 1945, 4000 boats have now been built. Their construction originally used molded plywood. The builders started using Glass-reinforced polyester or "fibreglass" in the late 1950s. The current hull configuration uses a glass-reinforced polyester molded boat with wooden rails, centre board trunk, thwart, fore grating, and aft grating. The spars were once made from spruce, but are now of entirely extruded aluminum construction.

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 extremely well in light wind. Their hulls have wide, rounded bottoms, allowing the boats to plane in winds as low as 10 knots. It is not uncommon to see thistles efficiently making their way, while other dinghys of similar design are becalmed.

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 fact, class rules do not limit crew weight. 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.

Mainsheet
The efficient 3:1 mainsheet system features a 40 mm switchable ratchet on the boom that can be turned to manage heavy loads. Easily opening and closing the leach at the top of the sail is considered the Thistle's single most important adjustment for maintaining optimum hull speed.

Mainsheet Traveler Control System
This 2:1 transom-mounted systems features low-profile track and traveler car rigged with top-mounted sheaves. Double-ended controls on the trunk cap allow crew to trim from the rail.

Vang
The 8:1 vang system ends at the center of the boat so it is easily accessible both upwind and downwind. Like any vang on a boat with a mainsail of such proportional power, vang tension helps control leach shape as measured by the top batten position, and allows the mainsheet to function as a secondary traveler.