Elmohamdy reunites with former boss Steve Bruce at Villa Park following spells under him at the KCOM Stadium and the Stadium of Light. He also becomes the third summer signing of the Claret and Blue Army in their bid to return to English top-flight.
''I am delighted to be here at Aston Villa,'' Elmohamdy told club website.
''Aston Villa is a great club and I am thrilled to join – it’s one of the very biggest clubs in England and its history and tradition is there for all to see.
''It’s a great time to join too as we look for promotion to the Premier League. “I will give absolutely everything to help us achieve that goal. "I know, first hand, what it takes to win promotion and I want that feeling again.''
The 29-year-old will now link up with the rest of the Villans squad in Germany ahead of the Cup of Traditions tournament.