Klaus Tonner was born in Hamburg in 1947. After studying law in Frankfurt/Main and Berlin, he was a research assistant at the University of Economics and Politics in Hamburg from 1972 to 1994, interrupted by teaching assignments at the Universities of Oldenburg, Hanover and Bremen. In 1980 he received his doctorate from the University of Hamburg.

In 1991, he habilitated at the University of Bremen. In 1994, he was appointed to the Jean Monnet Chair of Civil Law and European Law at the University of Rostock, which he held until his retirement in 2012. From 2006 to 2012, he was a part-time judge at the Rostock Higher Regional Court.

Klaus Tonner was Chairman of the Consumer Association Hamburg (1993-1997), Vice President of the German Society for Travel Law and is currently Vice President of the International Forum of Tour and Travel Advocates (IFTTA). He is co-editor of the legal journals "Verbraucher und Recht" and "Reiserecht aktuell".

His publications deal with consumer law, especially travel law. Main book publications: Travel Law in Europe, 1992; The Law of Time-sharing, 1997; The Travel Contract, 5th ed. 2007; Contract Law - Commentary, 2010 (co-editor with Armin Willingmann and Marina Tamm); Consumer Law - Advisory Handbook, 3rd ed. 2019 (co-editor with Marina Tamm); Law of Obligations: Contractual Obligations, 4th ed. 2015; The New Law of Obligations - Consumer Law Reform 2014 (co-editor with Tobias Brönneke), Online Mediation Platforms in Legal Practice, 2018 (co-editor with Peter Rott).