Refers to awareness of oneself as an individual, often in psychological or philosophical contexts. Can also imply being overly aware of how one appears to others.
Self-consciousness becomes stronger during adolescence.
He is very self-conscious and dislikes speaking in public.
自意識 is a near-synonym also meaning self-consciousness, but 自我意識 emphasizes the philosophical or psychological concept of self-awareness, while 自意識 is more commonly used for everyday self-consciousness.
自己意識 is another synonym, often used in academic contexts. 自我意識 carries a slightly more introspective or psychoanalytic nuance.
Compound of 自我 (self, ego) and 意識 (consciousness). 自我 is a Meiji-era coinage from Chinese-derived roots, and 意識 is a classical Buddhist term repurposed in modern psychology.