ATLAS measurements of collective, flow phenomena in a variety of collision systems, including pp collisions at 13 TeV, Xe+Xe collisions at 5.44 TeV, and Pb+Pb collisions at 5.02 TeV are presented. A measurement of the sensitivity of two-particle correlations in pp collisions to the presence of jets is presented. By rejecting particles associated with low-pT jets, this data can distinguish the role that semi-hard processes play in the collective phenomena observed in pp collisions. The correlation between the event-wise average transverse momentum ([pT]) and the harmonic flow (vn) carries important information about the initial-state geometry of the Quark-Gluon Plasma. Additionally, the potential quadrupole deformation in Xe+Xe is predicted to produce an initial state with enhanced shape and size fluctuations, and result in non-trivial change in the correlation. A new measurement of vn−[pT] correlations in Xe+Xe and Pb+Pb collisions is discussed for harmonics n=2, 3, and 4.