The chemistry and dynamics of melts and fluids at extreme conditions dictate the earliest thermal and chemical evolution of terrestrial interiors. Epochs of global magma oceans exist during planetary accretion and after giant impacts, resulting in the outgassing of volatiles to form an early atmosphere and differentiation of the silicate mantle to form an iron-rich core. At present day, melt and fluid behaviour remains crucial to understand the operation of the core and mass transfer near the core-mantle boundary. Understanding the material properties of melts and fluids under extreme conditions is thus fundamental to tackling a wide range of problems in Earth and planetary science. Although quantifying the behaviour of these materials poses theoretical and experimental challenges, new techniques and approaches as well as ever-increasing computational power are facilitating advances in our understanding. We therefore invite abstracts that shed light on the material properties and dynamic behaviour of melts and fluids at extreme conditions. We particularly encourage submissions that elucidate the properties and role of melts and fluids during early terrestrial planet accretion and evolution, and at conditions relevant to the lower mantle and core. As an interdisciplinary session, we encourage submissions from all disciplines of Earth and planetary science.