A samurai topknot is a popular men's hairstyle for men with mid-length to long hair and involves taking the hair and pulling it into a small bun at the top of the head. Most men wear the samurai topknot with the hair at the midpoint of the head down and the hair at the midpoint of the head up in the topknot.
The samurai topknot is essentially a standard bun and is sometimes called a "man bun" as well. The look originated in Japan with the samurai, hence the samurai topknot name. The look is often adapted by the hipster crowd or the young artsy business types. Buddha is also portrayed in many images as having worn a bun. Celebrities have also been sporting the look including Jared Leto, Leonardo DiCaprio, David Beckham, Brad Pitt and Bradley Cooper.
The Sikh topknot is another type of bun, but this look requires that the bun be placed on top of the head while a musician's ponytail is a low ponytail. Both looks can be adopted by men with longer hair. The samurai topknot is still popular in Japan where the creative hairstyles for men abound (Tokyo is particularly full of creative male hairstyles) and the look is likely to remain popular for men with longer hair for its ease and convenience.