Russia is a nation-state on the European and Asian continents on Earth. Moscow is both its largest and its capital city, and St. Petersburg is its second largest city. People or things originating from Russia are described as Russian.
Russians were amongst the passengers aboard the generational ship launched in the late 2040s that would colonize Hebron in 2096. (Star Trek: Shadowstar Station) Russians were amongst several groups who also left Earth in 2170 to protect their cultural identity. (Dominion War Timeline: "The Ramadan Offensive: Ash-Sham Sector: August-September 2375")
The 24th century Galaxy-class starship USS Nevsky (NCC-71038) was named after Saint Alexander Nevsky, a Russian military commander and statesman during the 13th century. (Last Unicorn RPG: The Dominion War Sourcebook: The Fires of Armageddon)