आचार, प्राचीन हिन्दू विधि (धर्म) की एक महत्वपूर्ण संकल्पना है जो किसी समुदाय या सामाजिक समूह के प्रथाओं को इंगित करता है। इसे सदाचार भी कहते हैं.

Ācāra is a concept used in the context of Classical Hindu law that refers to the customary laws or community norms of a particular social group. These community norms are delineated and put into practice by people who have earned the respect of those within each individual group, such as a community leader or elder. Although in Dharmaśāstra the ideal person who defines the ācāra of a particular place is dictated as one who knows the Vedas or is “learned”, in actual practice this role is often deferred to group leaders along with Vedic scholars. Ācāra is theologically important in Hindu law because it is considered, along with the Vedas (Śruti), and Smriti, to be one of the sources of dharma. Particular regional ācāra is believed to be canonized in Dharmaśāstra texts; however scholars differ on the source for the actual accounts found within these texts.