3015 20170106120004.0 10.1007/s11207-016-1017-8 DOI SCART-2017-0011 Clette, F. Preface to Topical Issue: Recalibration of the Sunspot Number 2016 Topical Issue: Recalibration of the Sunspot Number This topical issue contains articles on the effort to recalibrat e the sunspot number (SN) that was initiated by the Sunspot Number Workshops. These workshops led to a revision of the Wolf sunspot number (WSN) and a new construction of the group sunspot number (GSN), both published herein. In addition, this topical issue includes three independently proposed alternative SN time series (two Wolf and one group), as well as articles providing historical context, critical assessments, correlative analyses, and observational data, both historical and modern, pertaining to the sunspot-number time series. The ongoing effort to understand and reconcile the differences between the various new sunspot number series is briefly discussed. STCE Cliver, E. W. Lefèvre, L. Svalgaard, L. Vaquero, J. M. Leibacher, J. W. Solar Physics 291 2016 9-10 2479-2486 laure.lefevre@observatoire.be published in REFERD