Recent progress on the worldwide development of gyrotrons for fusion application is presented. After breakthroughs of gyrotron technologies in the 1990s, significant progress has been made in the 2000s, in particular, on a long-pulse gyrotron for a wide range of frequencies from 84 to 170 GHz. And, activities for advanced gyrotrons, for example, a high-power gyrotron using a coaxial resonator, a multifrequency gyrotron, etc., have proceeded. With this progress have come improvements of gyrotron components such as a high-efficiency mode converter, a wide-band window, etc. The gyrotrons have been applied to major fusion devices for heating and magnetohydrodynamics controls. At present, the development of a 1-MW-class continuous-wave gyrotron is in the scope, which is applicable for the self-ignition experiment of fusion plasma and its confinement at the International Thermonuclear Experimental Reactor (ITER).