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.

The Malay world or Malay realm is a concept or an expression that has been used by different authors and groups over time to denote several different notions, derived from varied interpretations of 'Malay' either as an ethnic group, as a racial category, as a linguistic group or as a cultural group. The use of the term Malay in much of the conceptualisation is largely based on the prevalent Malay cultural influence, manifested in particular through the spread of the Malay language in Southeast Asia as observed by different colonial powers during the Age of Discovery and spread of Islam. The term remains highly controversial in Indonesia and outside the Malay-speaking areas, because it is considered politically charged and irredentist rather than purely cultural.