ggraph plots network graphs using the conventions and power of ggplot2
igraphis a collection of network analysis tools with the emphasis on efficiency, portability, and ease of use. igraph is open source and free, and can be used in R, Python, and C++
network (pdf) manages relational data in R. Networks can be created with any combination of undirected/directed, valued/unvalued, dyadic/hyper, and single/multiple edges
networkD3 creates D3 JavaScript network, tree, dendrogram, and Sankey graphs
tidygraph conceptualizes a network graph as two tidy data frames consisting of node and edge data
igraph is a package to manipulate and analyze graphs and networks. It can be used to create, manipulate, and analyze networks; convert graphs to/from networkx, graph-tool, and many file formats; and plot networks. Read the documentation and a tutorial.
networkx is a package for the creation, manipulation, and study of the structure, dynamics, and functions of complex networks. Read the documentation and a tutorial. Other resources: