This document announces a special issue of the journal Future Generation Computer Systems on machine learning and knowledge graphs. The issue calls for communities related to machine learning, deep learning, and knowledge graphs to develop more effective algorithms and applications by joining forces. Papers are due November 30, 2019 with final review decisions by July 31, 2020. The guest editors are Mehwish Alam, Anna Fensel, Jorge Martinez-Gil, Bernhard A. Moser, Diego Reforgiato Recupero, and Harald Sack.