With over 20 years of experience in player skill development, his notable coaching career includes stints with USA Rugby, the New Zealand Women's squad and clubs in Argentina.
Through his contract work and his role at the International Rugby Academy, Ellis has become internationally recognised as an innovative technical coach who gets results.
His ability to maximise skill development in players has meant he is in demand throughout the world as a skills specialist.
Connacht head coach Pat Lam, who has worked with Ellis in the past, said: "The biggest thing with Dave is his massive ability as a coach around skills, decision making and player development.
"The last 10 years he's been involved with the International Rugby Academy in New Zealand where I worked with him, and I saw the ability he had in improving not only players but also some of the best international coaches in the world.
"I've been working closely with Tom Sears and the PGB (Professional Game Board) over the last few months to ensure we get the right staff and they've been very supportive.
"I've been so pleased with the quality of coaches here at Connacht - Dan (McFarland), Nigel (Carolan), Jimmy (Duffy), and Cory (Brown). Dave meets that criterion of being a good team man.
"His knowledge of the game, ability to get his message across, planning and attention to detail is top class and I know he'll be a big asset for Connacht and Irish rugby."
Ellis himself admitted: "I look forward to joining the team at Connacht and working with Pat again.
"I am excited by the innovative systems used at Connacht and hope I can add value to an already flourishing programme."