Klemens Wilhelm Jacob Meckel (28 March 1842 – 5 July 1906) was a general in the Prussian army and foreign advisor to the government of Meiji period Japan.

Meckel was born in Cologne, Rhine Province, Prussia and joined the Prussian Army in 1860 as part of the 68th Infantry Regiment.

He is credited with having introduced Clausewitz's military theories[5] and the Prussian concept of war games (Kriegspiel) in a process of refining tactics.

[6] By training some sixty of the highest-ranking Japanese officers of the time in tactics, strategy and organization, he was able to replace the previous influences of the French advisors with his own philosophies.

[8] However, Meckel's tactical over-reliance on the use of infantry in offensive campaigns was later considered to have contributed to the large number of Japanese casualties in the subsequent Russo-Japanese War of 1904–1905.