The Belgian Nuclear Research Centre (SCK•CEN) is at the forefront of heavy liquid-metal (HLM) nuclear technology worldwide with the development of the Multi-purpose hYbrid Research Reactor for High-tech Applications (MYRRHA) accelerator-driven system. MYRRHA is a flexible fast-spectrum pool-type research reactor cooled by lead bismuth eutectic (LBE) and has been identified as the European Technology Pilot Plant for the lead-cooled fast reactor. Given the innovative nature of MYRRHA, the project is currently going through a prelicensing phase. The MYRRHA research and development (R&D) program is driven by this prelicensing process and aims to fill the existing gaps in knowledge with respect to LBE chemistry, material behavior, fuel behavior, instrumentation, and HLM thermal hydraulics. In this critical review we present selected topics from the R&D program on HLM thermal hydraulics that are essential for the design, engineering, and safety analysis of MYRRHA and other HLM-cooled reactors. The topics addressed include turbulent heat transfer in HLM, fuel assembly thermal hydraulics and flow-induced vibrations, control rod hydrodynamics, primary heat exchanger pool and integral system thermal hydraulics, sloshing, and multiphysics modeling.