The aim of this workshop is to bring together researchers working on objective Bayesian methodology, nonparametric Bayesian methods and machine learning. Objective Bayesian methods are evolving from a historically narrower focus on issues related to prior specification to research themes that are more broadly related to default methods in Bayesian statistical analysis. This naturally leads to an increasing overlap with Bayesian nonparametric modeling and machine learning. The workshop seeks to exploit this increasing intersection by bringing together participants from all three research communities.