Counter Unmanned Aircraft Systems (C-UAS) protect critical assets and events against UAS threats. UAS are being used in various conflicts around the world and have the potential to be used domestically in the US. An important objective of Department of Homeland Security (DHS) and the Department of Defense (DoD) is to cost-effectively field C-UAS capabilities that will protect these critical assets against UAS threats. This workshop will host a keynote speaker and sponsor plenaries who will create a foundational understanding of the C-UAS threat profile and ongoing efforts to field C-UAS capabilities. From this, our workshop will share information and analysis used in support of C-UAS requirements development, acquisitions, and deployment, concentrating on how to address 1) mission effectiveness estimation and assessment, 2) cost estimation, and 3) development of UAS risk analysis measures and techniques. This workshop will target DoD and DHS Requirements, Acquisition, Risk Analysis, Program Analysis and Operational Analysis communities.