Abstract: A fountain pen is provided with a tubular barrel, and ink guide with a nib on its front end and a cartridge on its rear end. The ink guide is mounted so that it is substantially linearly movable not only between a writing position in which the tip of the nib projects out of the front end of the barrel, and a storage position in which the nib is retracted within the barrel, but also a replacement position in which the rear end of the cartridge projects out of the open rear end of the barrel so that the cartridge can be readily grasped for replacement. A cover cap may be provided with an axially extending support pin having a free end which engages a pivotal closure cap to prevent it from opening the rear end of the barrel as a result of pressure exerted by the ink cartridge. The free end of the support pin also engages the ink guide, when the pen is in the writing position and the cover cap surrounds the front end of the barrel, to insure that the tip of the nib is spaced from all portions of the cover cap.