On August 24, 1991, Ukraine followed suit, launching itself on a rocky journey.
For years, the country swung between leaders who favored Moscow and those who looked towards the West, twice ousting pro-Russian leaders with mass demonstrations.
Then, in 2014, Russia annexed Crimea, and pro-Russian troops seized of a big chunk of south-eastern Ukraine.
Ukraine's economic health took a big hit when the Soviet Union collapsed, bottoming out in the late 1990s. Over the next decade it clawed its way back, before being whacked by the global financial crisis; it took another blow when war broke out on the border with Russia.
Ukraine is showing steady improvement in one area: life expectancy.
It dropped sharply in the wake of the Chernobyl nuclear explosion in 1989, but has mostly been rising since 1995.
Even here, though, the war in the east is taking a toll: after nearly a decade of improving figures, there was no increase from 2013 to 2014 -- the year the war began.
What now for Ukraine?
Andrey Slusharenko, 32, of Kiev, is one of the Ukrainian troops are fighting to regain control of their territory. He thinks Ukraine achieved its independence too easily, but that more than two years of war have driven home a difficult lesson.
"We weren't an independent country before. We had a pro-Russian government, a pro-Russian president," he said.
"What independence meant, we understand now ... I think we wasted a lot of time these 25 years."