The Windsor knot, also referred to as a Full Windsor or as a Double Windsor to distinguish it from the half-Windsor, is a method of tying a necktie around one's neck and collar. The Windsor knot, compared to other methods, produces a wide symmetrical triangular knot. The knot is often thought to be named after the Duke of Windsor. It was, however, likely invented by his father George V.

The Windsor knot, sometimes referred to as a full Windsor to distinguish it from the half-Windsor, is a knot used to tie a necktie. As with other common necktie knots, the Windsor knot is triangular, and the wide end of the tie drapes in front of the narrow end. The Windsor is a wider knot than most common knots, and while not truly symmetric is more balanced than the common four-in-hand knot. The Windsor's width makes it especially suited to be used with a spread or cutaway collar.