This book constitutes the refereed proceedings of the First International Rapid Mashup Challenge, RMC 2015, held on June 23, 2015, in Rotterdam, The Netherlands, in conjunction with the 15th International Conference on Web Engineering, ICWE 2015. The 2015 edition of the challenge is the first installment of a series of challenges that aim to engage researchers and practitioners in a competition for the best mashup approach. The 6 thoroughly reviewed contributions contained in this volume are extended versions of the initial proposals that served the authors to express their interest to participate in the challenge. The initial proposals have been used by the challenge organizers to select participants based on the interestingness and maturity of the proposals.