We isolated and described a yellow-pigmented strain of bacteria (strain 9143^T), originally characterized as an endohyphal inhabitant of an endophytic fungus in the Ascomycota. Although the full-length sequence of its 16S rRNA gene displays 99 % similarity to Luteibacter pinisoli, genomic hybridization demonstrated <30 % genomic similarity between 9143^T and its closest named relatives, further supported by average nucleotide identity results. This and related endohyphal strains form a well-supported clade separate from L. pinisoli and other validly named species including the most closely related Luteibacter rhizovicinus. The name Luteibacter mycovicinus sp. nov. is proposed, with type strain 9143^T (isolate DBL433), for which a genome has been sequenced and is publicly available from the American Type Culture Collection (ATCC TSD-257^T) and from the Leibniz Institute DSMZ (DSM 112764^T). The type strain reliably forms yellow colonies across diverse media and growth conditions (lysogeny broth agar, King’s Medium B, potato dextrose agar, trypticase soy agar and Reasoner's 2A (R2A) agar). It forms colonies readily at 27 °C on agar with a pH of 6–8, and on salt (NaCl) concentrations up to 2 %. It lacks the ability to utilize sulphate as a sulphur source and thus only forms colonies on minimal media if supplemented with alternative sulphur sources. It is catalase-positive and oxidase-negative. Although it exhibits a single polar flagellum, motility was only clearly visible on R2A agar. Its host range and close relatives, which share the endohyphal lifestyle, are discussed.