Marcus Tandler, also known as the Mediadonis, is a partner at the German-based online marketing company Tandler.Doerje.Partner, which provides SEO services to large companies and websites looking to improve their rankings within the Google guidelines. Together with his partner, former Google employee Niels Doerje, Tandler consults for various large companies across Europe about all aspects of online marketing.

Marcus was a co-host of the popular Webmasters on the Roof show on Webmasterradio.FM. He received a lectureship at the Fachhochschule Erding, and lectured several times at the University of Darmstadt on how to excel in online marketing. Tandler received the Outstanding Personal Contribution to Affiliate Marketing Award at CJU Europe in 2007, becoming the first German to receive this award.