**Our apologies if you receive multiple copies of this CFP** *CALL FOR PAPERS* for the PhD forum at the European Conference on Machine Learning and Principles and Practice of Knowledge Discovery in Databases (ECML PKDD 2021), Bilbao, Spain. *SCOPE AND MOTIVATION* The premier European machine learning and data mining conference (ECML PKDD) includes a PhD student forum on machine learning and knowledge discovery. During the forum, researchers with experience in supervising and examining doctoral students will participate and provide constructive feedback and advice to the participants. This is an excellent opportunity for developing person-to-person networks to the benefit of the PhD students in their future careers. The criterion for acceptance: the submission is clearly structured and written and is of sufficient maturity to enable the advisors to provide constructive feedback. Papers will not be formally published. However, unless the authors opt out, they will be made publicly available through the conference website. *IMPORTANT DATES* - Submission deadline: June 21, 2021. - Notification of Acceptance: July 12, 2021. - PhD Forum: September 13, 2021. For more information see https://2021.ecmlpkdd.org/?page_id=1591 We look forward to welcoming you in Bilbao.