Actin is the most abundant cytosolic protein in eukaryotes where it plays essential roles in a variety of ubiquitous processes including cell and organelle motility, cytokinesis, endocytosis, and muscle contraction. Central to actin’s function is its ability to transition between monomeric (G-actin) and filamentous (F-actin) forms. Each actin subunit within F-actin is orientated in the same direction, affording structural and kinetic polarity to the filament; the ‘barbed’ (or +) end grows severalfold faster than the ‘pointed’ (or -) end in cells. This asymmetry underlies many actin-based processes; the barbed end is directed toward cellular membranes so that its fast growth can generate protrusive forces that reshape the membrane while the pointed end is directed away and loses subunits so that they may be recycled for incorporation at the barbed end. In turn, numerous regulatory proteins converge at the ends to fine-tune F-actin assembly and disassembly dynamics through diverse and poorly understood mechanisms. In this work, we developed a strategy for determining structures of actin filament ends, both alone and bound to several different effectors, using cryogenic electron microscopy (cryo-EM). Structures of the unbound barbed end pointed ends reveal conformational differences in terminal actin subunits that are favorable for subunit association and dissociation, respectively. Structures of the barbed and pointed ends bound to CapZ and tropomodulin, respectively, show how these so-called ‘capping proteins’ block subunit exchange. Structures of the barbed end bound to formins and profilin reveal a stepwise mechanism for formin-mediated acceleration of barbed end elongation. Structures of the barbed end bound to gelsolin reveal its mechanism of F-actin severing and subsequent barbed end capping. Finally, we determined the cryo-EM structure of CARMIL bound to CapZ which, coupled with biochemical studies, reveals how CARMIL reduces the affinity of CapZ for the barbed end. Together, these studies substantially advance foundational understanding of actin filament end regulation by diverse and unrelated proteins.