noun
documentary film
A non-fiction motion picture intended to document reality, primarily for instruction, education, or maintaining a historical record.
昨夜、環境問題についてのドキュメンタリー映画を見た。
Last night I watched a documentary film about environmental issues.
A broader term that can refer to a documentary film, TV program, or even a book; ドキュメンタリー映画 specifically denotes a film.
Wasei-eigo compound from English 'documentary' + 映画 (film).