An ink supply system includes an ink cartridge and an cartridge accommodating portion. An ink cartridge includes a cartridge case forming an ink chamber, an ink supply portion, and an air intake portion. The cartridge case includes a front face, a rear face opposite the front face, and a particular face connected to each of the front face and the rear face. The particular face has an opening formed therethrough. The ink supply portion is positioned at the front face and configured to supply ink. The air intake portion is configured to introduce air from the outside of the ink cartridge to the ink chamber. The air intake portion includes a valve, a valve seat, an urging, and an operation member. The cartridge accommodating portion has an accommodating chamber having a wall contacting an operation member.