Legislatures are naturally interactive institutions. Creating laws, engaging in representation and oversight, and serving constituents are social processes. Legislators have many connections with each other, some preexisting or natural and some created while in office. This chapter explores various ways to understand legislative politics through a relational lens. Legislators rely on networks for a variety of functions, including collaboration, information diffusion, policy coordination, coalition building, and voting. Relationships are a fundamental aspect of how legislators, and those who interact with them, function. The chapter examines the history of how networks have been studied in legislatures and describes various challenges this field of study has recently overcome, as well as other challenges yet to be solved in studying legislative politics using networks. It relays the dominant existing applications and methods in this subfield and suggests several fruitful avenues for future research.