In the science fiction of Cordwainer Smith, the Instrumentality of Mankind refers both to Smith's personal future history and universe and to the central government of humanity. The Instrumentality of Mankind is also the title of a paperback collection of short stories by Cordwainer Smith published in 1979 (now superseded by the later The Rediscovery of Man, which collects all of Smith's short stories).
In the history of Cordwainer Smith's "Instrumentality" universe, the Instrumentality originated as the police force of the Jwindz or "perfect ones" on a post-nuclear-holocaust Earth. After attaining power and the expansion of humans in space, they eventually entered a somewhat stagnant phase in which a fixed lifespan of four hundred years was imposed on the human inhabitants of the planets where the Instrumentality directly ruled, all the hard physical labor was done by rightless animal-derived "underpeople", and children were never raised by their biological parents. This somewhat empty and sterile system was reformed and enlivened by the "Rediscovery of Man", the backdrop against which Smith's novel Norstrilia and the majority of his short stories, covering thousands of years of fictional time, are set. The cycle does not come to a final resolution (there were hints dropped about a mysterious trio of "robot, rat, and Copt" which were not followed up, possibly because of Smith's own death).
Though the Instrumentality does not directly administer every planet, it claims ultimate guardianship over the destiny of the human race. For example, it strictly bans the export of religion from planet to planet. Its members, the Lords and Ladies of the Instrumentality, are collectively all-powerful and often somewhat callously arbitrary. Although their motives are genuinely benign, they act with utmost brutality when survival is at stake.
Here is an explanation from the story "Drunkboat":
Some prominent Lords and Ladies of the Instrumentality:
The names Goroke, Femtiosex, Sto Odin and Panc Ashash are number-word names of the type common during the Instrumentality's decadent period: "five-six" in Japanese is Go-Roku, in Hindi it is Panc-Ashash, and in Swedish Femtiosex (literally "fifty-six"). 'Tiga-belas' and 'Veesey-koosey', the names of supporting and main characters of the Instrumentality story Think Blue, Count Two, also mean 'thirteen' (Indonesian or Malay tiga meaning three, and belas being equivalent of English "teen") and 'five-six' (Finnish viisi and kuusi), respectively. Sto Odin is "a hundred and one" in Russian. The name Jestocost is based on the word for "cruelty" in Russian (жестокость), and Crudelta is the equivalent in Italian (crudeltà, feminine). Gnade is a German word meaning "grace" or "mercy".