Louis Paulsen (15 January, 1833 - 18 August, 1891) was a German chess player.

In the 1860s and 1870s he was regarded as one of the five best players in the world. He was Wilfired Paulsen’s younger brother.

He was one of the first players, who possessed the opinion that an attack could be constructed brilliantly. Putting forward the idea, he drew a conclusion: any excellent attacks are not successful against a correct defence. Paulsen’s ideas were grasped by Wilhelm Steinitz, who claimed the attack and defence have equal status. Aron Nimzowitsch considered Paulsen one of the six greatest "purely defensive players".

Paul Morphy and Paulsen were the first Masters of the game and of blindfold chess. They were able to play 10 blindfold games at the same time, without major faults.

In 1962 Paulsen challenged Adolf Anderssen for the world championship title. The match ended with a tie (4-4), Anderssen remained the unofficial world champion. Paulsen later defeated Anderssen twice, in 1876 and 1877.

He made many contributions to the opening theories, such as the Sicilian Dragon, the Sicilian Paulsen variation, French Defense Paulsen Attack and Vienna Game Paulsen variation.

„Paulsen Pawns is a term coined by Nimzowitsch for a restricted pawn centre with two pawns on squares d6 and e6 for Black or d3 and e3 for White, often coupled with an open c-file. This restricted centre makes it difficult for the opponent to whip up a quick attack by advancing his centre. Paulsen pawns are the stalwart of the Paulsen Variation of the Sicilian Defence.” (Wikipedia)

The modern form of the Sicilian Dragon came from Paulsen, from the 1880s. Henry Bird often used this, then, at about 1900 its use became generally accepted. The Dragon variation belonged to the main lines of the Sicilian Defence.

According to Chessmetrics historical rating Paulsen ranked on the top of the world ranking list between April 1862 and July 1878 in 39 different months, achieved his highest score in October 1962, having 2710 points.