The ITU AI/ML in 5G Challenge aims to provide a platform for collaboratively addressing the problems in applying AI/ML in future networks including 5G. The 2021 edition of the Challenge connected more than 1600 participants from 82 countries, with industry and academia solving real-world problems using AI/ML in networks. The Challenge offers carefully curated problem statements, a mix of real-world and simulated data, technical webinars, mentoring, and hands-on-sessions. Teams participating in the Challenge enable, create, train and deploy ML models for communication networks. This enables participants to not only showcase their talent, test their concepts on real data and real-world problems, and compete for global recognition, but also enter the world of ITU standards by mapping their solutions to our specifications.