There are a few hundred known sign languages around the world, and in such language communities, multilingualism is the norm. This multilingualism traverses modalities: signed, written, and, in some cases, spoken forms of language. Such a linguistic landscape inevitably leads to various forms of language contact between languages, including contact between two or more signed languages (characterised by lexical borrowing), signed language and spoken language (characterised by mouthings), and signed language and written language (characterised by fingerspelling, initialized fingerspelling). This chapter also covers sign language interference, code switching and code mixing, and the concept of bimodal bilingualism. The chapter concludes with a discussion of pidginization and creolization of sign languages and sign language endangerment, as well as general comments on the characteristics of contact between signed languages.