Malayisation or Malayization is a process of assimilation and acculturation, that involves acquisition or imposition of elements of Malay culture, in particular, Islam and the Malay language, as experienced by non-Malay populations of territories fully controlled or partially influenced by historical Malay sultanates and modern Malay-speaking countries. It is often described as a process of civilisational expansion, drawing a wide range of indigenous peoples into the Muslim, Malay-speaking polities of Maritime Southeast Asia. Examples of Malayisation have occurred throughout Asia including in Brunei, Cambodia, Indonesia, Malaysia, Singapore, and Sri Lanka.

Malayness is the state of being Malay or of embodying Malay characteristics. This may include that which binds and distinguishes the Malay people and forms the basis of their unity and identity. People who call themselves Malay are found in many countries in Southeast Asia, united by a notional shared identity but divided by political boundaries, divergent histories, variant dialects and peculiarities of local experience. While the term 'Malay' is widely used and readily understood in the region, it remains open to varying interpretations due to its varied and fluid characteristics. 'Malay' as an identity, or nationality, is considered one of the most challenging and perplexing concepts in the multi-ethnic world of Southeast Asia.