He has replaced Olly Foot, who was promoted to joint chief executive alongside Chris Whitson last year.
Conner joined the Interpublic agency from OgilvyOne in 2014 and is credited with playing a key role in winning new business such as easyJet, Pernod Ricard and TSB.
Foot said: "Matt has already proven himself to be a very versatile leader, he really understands our clients’ businesses and he has an incredible amount of passion for ours."
Following the leadership departures of Meteorite founders Hugh Bishop and Debbie Smith, MRM Meterorite is now run as a triumvirate between Foot, who is also chief commercial officer, Whitson (also chief strategy officer), and Nicky Bullard, chairman and chief creative officer.
The direct and digital agency was formed in 2011 when Meteorite was sold to McCann Worldgroup and merged with McCann Relationship Marketing.