The 28-year-old joins the Royals on a free transfer with the Berkshire team his second club in England following a spell with Fulham last season.
Director of football Nick Hammond said: "We were always hopeful that a permit would be secured but it's still great to get the deal done. It'll be nice get him in and working with the lads - he's a great individual, and will fit really well into group."
His goalscoring form earned Pogrebnyak a move to Zenit St Petersburg where he guided them to the league title as well as the 2008 UEFA Cup final against Rangers although he missed the game in Manchester due to suspension.
He moved on to Stuttgart where he spent three years before joining Fulham in January 2012 until the end of the season and the Cottagers were apparently keen to tie the Russia international to a permanent contract after he scored six goals in 12 appearances.