This book constitutes the refereed proceedings of the 26th British National Conference on Databases, BNCOD 26, held in Birmingham, UK, in July 2009.The 12 revised full papers, 2 short papers and 5 poster papers presented together with 2 keynote talks, 2 tutorial papers and summaries of 3 co-located workshops were carefully reviewed and selected from 33 submissions. The papers are organized in topical sections on data integration, warehousing and privacy; alternative data models; querying; and path queries and XML;data mining and privacy, data integration, stream and event data processing, and query processing and optimisation.