Advanced Photonics and its sibling journal Advanced Photonics Nexus welcome submissions to a joint theme issue on orbital angular momentum (OAM) and its association with optical science and applications. The theme issue is dedicated to the 30th anniversary of Professor Allen’s paper published in Physical Review A in 1992, where laser light with a Laguerre-Gaussian amplitude distribution was found to have an OAM. Since then, conceptual studies on OAM have attracted great attention in physics and optics communities for many years. In recent years, the world has witnessed birth and development of novel and break-through technologies originally driven by the OAM, from novel light manipulation to significant applications in super resolved microscopy, lithography, optical communication, and others. In this connection, we are honored to organize the theme issue to pay our respect to Professor Allen for his pioneering study on OAM, as well as great achievements by other scientists and scholars in this field.