This paper describes the optical design of the general-purpose Spanish beamline for absorption and diffraction (SpLine), which will be installed on a bending-magnet port of the ESRF. This beamline is planned to cover the needs of the Spanish synchroton radiation community with broad scientific fields of interest, covering physics, chemistry, materials science and biology. By using the advantages of a wide front end (9 mrad), the Spanish beamline will be split into two branches. Both branches will be equipped with focusing optics and experimental stations. Thus, each branch can be operated simultaneously and independently from each other. One branch (A) will have two experimental stations, one for high-resolution powder diffraction (HRPD) and the other for X-ray absorption spectroscopy (XAS) and X-ray standing waves (XSW). The other branch (B) will have facilities for macromolecular crystallography and for single-crystal diffraction analysis, including that of surfaces and interfaces, as well as an X-ray diffraction/scattering camera for non-crystalline specimens.