Provided are an endoscope illumination optical system and an endoscope optical system unit that can change the irradiation direction of illumination light in two directions without bending the endoscope even in a narrow space. In an endoscope illumination optical system 10 having a light emitting unit 11 and a first optical path deflecting prism group PG1 that takes in illumination light emitted from the light emitting unit 11 and deflects the optical path to irradiate the subject, the first optical path deflecting prism 10 The group PG1 includes three prisms, a first prism P1, a second prism P2, and a third prism P3, in order from the subject side. The first prism P1, the second prism P2, and the third prism P3 are mutually connected. The first prism P1 is arranged in proximity to the second prism P2, and the rotation direction of the first prism P1 is changed to change the illumination light irradiation direction A to the first direction DR1. The first prism P1 and the second prism P2 The irradiation direction A of illumination light can be changed to a second direction DR2 different from the first direction DR1 by rotating the prism integrally with respect to the third prism P3.狭い空間においても内視鏡を湾曲させずに照明光の照射方向を２方向に変えることができる内視鏡照明光学系及び内視鏡光学系ユニットを提供する。 発光部１１と、発光部１１から出射した照明光を取り込み、光路を偏向させて被写体に照射する第１光路偏向プリズム群ＰＧ１と、を有する内視鏡照明光学系１０において、第１光路偏向プリズム群ＰＧ１は、被写体側から順に、第１プリズムＰ１と、第２プリズムＰ２と、第３プリズムＰ３と、の３つのプリズムからなり、第１プリズムＰ１、第２プリズムＰ２、第３プリズムＰ３は互いに近接して配置され、第１プリズムＰ１が第２プリズムＰ２に対して回転移動することで照明光の照射方向Ａを第１方向ＤＲ１に可変とし、第１プリズムＰ１と第２プリズムＰ２の２つのプリズムを一体として第３プリズムＰ３に対して回転移動することで照明光の照射方向Ａを第１方向ＤＲ１とは異なる第２方向ＤＲ２に可変とする。
