Dye chemistry is a traditional and highly interdisciplinary research area in organic chemistry. Specifically, the synthesis, experimental and theoretical investigation, as well as the application of organic dyes contribute significantly to several disciplines in chemistry. In this context, recent progress in organic synthesis and highly sophisticated physical–chemical or analytical methods led to a renaissance of dye chemistry; as specifically designed dyes are required to fulfil the special requirements to be employed in, for example, high-resolution microscopy, fluorescence spectroscopy, photovoltaics or OLED materials. Hence, this thematic issue of the Beilstein Journal of Organic Chemistry aims to cover the diverse modern aspects of organic dye chemistry that range from the traditional disciplines, namely synthesis and investigation of photophysical properties, to applications in spectroscopy, sensing, (bio)analytical chemistry, materials science, biology, and industry.