Takasugi Shinsaku (高杉 晋作, 27 September 1839 – 17 May 1867) was a samurai from the Chōshū Domain of Japan who contributed significantly to the Meiji Restoration.

Takasugi, in spite of his young age, was an influential factor within Chōshū as one of the most extreme advocates of a policy of seclusion and expelling the foreigners from Japan.

In spite of Japan's policy of national isolation in the Edo period, in 1862 Takasugi was ordered by the domain to go secretly to Shanghai in Great Qing Empire to investigate the state of affairs and the strength of the Western powers.

Takasugi clearly saw that utilization of the financial wealth of the middle-class merchants and farmers could increase the military strength of the domain, without weakening its finances.

Since the leaders of Chōshū were unable - and unwilling - to change the social structure of the domain, limited use of peasants and commoners enabled them to form a new type of military without disturbing the traditional society.

In June 1863, Takasugi himself founded a special Shotai unit under his direct command called the Kiheitai, which consisted of 300 soldiers (about half of whom were samurai).

In September 1864, a fleet of warships of British, French, Dutch and American naval forces attacked Shimonoseki again and occupied the gun battery there.

Their fighting against Chōshū units demonstrated the inferiority of traditional Japanese troops against a Western army, and convinced the leaders of the domain of the absolute necessity for a thorough military reform.

The Chōshū domain's administration called on Takasugi not only to carry out this reform as ‘Director of Military Affairs’, but he - only 25 years of age - was also entrusted with negotiating peace with the four Western powers.

Takasugi reorganized his Kiheitai militia into a rifle-unit with the latest modern rifles, and introduced training in Western strategy and tactics.

Takasugi, with only about a dozen followers, including future political leaders Yamagata Aritomo, Itō Hirobumi and Inoue Kaoru, gathered in Kokura in Kyūshū and prepared an attack on the conservative forces in Chōshū.

Takasugi played a major role in this civil war and his former Kiheitai militia proved its superiority over old-fashioned samurai forces.

Around February 1867, his wife Masa and their three year-old son Tōichi [jp] (aka Takasugi Umenoshin) (1864–1913) arrived from Hagi to visit him.

However in March 1867, Takasugi's illness worsened yet again, Masa and Tōichi were summoned back to Hagi, while Baisho and Nomura stayed with him until his death on 17 May 1867.

Only a year later, Takasugi's dream of overthrowing the Tokugawa Shogunate, which found obvious manifestation in his nickname Tōgyō (東行), was fulfilled with the Meiji Restoration.