Common Law, Civil Law, and Colonial Law builds upon the legal historian F.W. Maitland's famous observation that history involves comparison, and that those who ignore every system but their own 'hardly came in sight of the idea of legal history'. The extensive introduction addresses the intellectual challenges posed by comparative approaches to legal history. This is followed by twelve essays derived from papers delivered at the 24th British Legal History Conference. These essays explore patterns in legal norms, processes, and practice across an exceptionally broad chronological and geographical range. Carefully selected to provide a network of inter-connections, they contribute to our better understanding of legal history by combining depth of analysis with historical contextualization. In particular, my chapter intends to shed some light on the history of comparative commercial law. Legal historiography has pointed out the importance of a comparative approach in the history of commercial law. My point is slightly different: my research focuses on the role of comparative studies in the history of commercial law. More precisely, I focus on the comparative argument in the 19th century commercial law discourse, and I study Leone Levi (1821-1888) and his comparative commercial law works. Leone Levi was an Italian-born merchant who became jurist, statistician and economist in Victorian Britain. His eclectic personality, together with his strong commitment in a large number of juridical, economical and statistical issues is fascinating in itself. My purpose is to present Levi’s contribution to 19th century commercial law, in particular his comprehensive treatise on Commercial Law of the world published in 1850-1852. The treatise was reprinted in 1863 under a different title: International commercial law : being the principles of mercantile law of the following and other countries, viz.: England, Scotland, Ireland, British India, British colonies, Austria, Belgium, Brazil, Buenos Ayres, Denmark, France, Germany, Greece, Hans Towns, Italy, Netherlands, Norway, Portugal, Prussia, Russia, Spain, Sweden, Switzerland, United States, etc.). In synthesis, commercial law tends naturally to comparison because trades and commerce are transnational by nature: commercial law scholars and practitioners share very often a comparative and transnational point of view. The aim of my essay is to discuss in what way and to what purpose a 19th century sui generis commercial lawyer – i.e. Leone Levi – made use of comparative law in dealing with commercial and business legal matters.