Ultra-high-performance concrete (UHPC) is attracting increasing interests worldwide due to its superior mechanical properties and durability. Securing proper rheological properties can affect fiber dispersion and alignment with marked effect on UHPC performance. Tailoring the rheological properties of UHPC to secure enhanced performance is not widely considered in the mixture design stage. In this paper, an overview of the rheological properties of UHPC, applicable flow models, measurement techniques and errors associated with the interpretation of rheological measurements are discussed. The effect of various constituent materials on rheological properties of UHPC is presented. This includes the cementitious materials, sand, chemical admixtures, fibers, nanomaterials, and internal curing agents. Most importantly, the paper discusses the rheological properties requirements of UHPC and strategies to control rheology of UHPC targeted for different applications, such as repair and rehabilitation, bridge deck panel connections, construction of structural and architectural elements, and digital fabrication.