Lensless ultrathin fiber-optic endomicroscopic imaging technology based on multimode fiber or multicore fiber has made great progress in recent years, and it is expected to produce the next-generation ultra-minimal high-resolution endoscope. By spatiotemporally controlling the coherent incident light field, the influence of mode dispersion in multimode fibers or phase distortion in multicore fibers can be overcome. High-resolution focusing, imaging, and related applications can be achieved through optical fibers without using lens or scanning device at the distal end. In addition, in scenarios of lensless fiber-optic endoscopic imaging or image transmission, object information reconstruction can be achieved from the output measurements by building a physical or deep learning model. This article reviews the development of coherent optical fiber lensless imaging technology. First, it depicts the basic working principles of lensless optical fiber imaging and the imaging methods from the two perspectives of active wavefront control and passive object reconstruction. Then it introduces some advanced optical fiber imaging modalities and technologies and lists fiber imaging related applications, with discussions of general challenges encountered in this field. Finally, a brief summary is made with envision of the development roadmaps.