An ink cartridge includes a cartridge body including an ink storage chamber and a wall having an ink introduction hole formed therethrough. The ink introduction hole is configured to receive an ink supply tube of an inkjet printer when the ink cartridge is mounted to the inkjet printer, and the ink supply tube is configured to communicate with an ink supply channel of the inkjet printer via a communication path. The ink cartridge also includes a first valve member configured to selectively open and close the ink introduction hole, and a first urging member configured to apply a first force to the first valve member to urge the first valve member to close the ink introduction hole. The first valve member includes a valve body configured to receive a second force from the ink supply tube when the ink cartridge is mounted to the inkjet printer. The second force urges the first valve member to open the ink introduction hole, and the second force is greater than the first force. The first valve member also includes a projecting portion which projects from the valve body in a predetermined direction toward the exterior of the ink storage chamber via the ink introduction hole. The projecting portion is configured to enter the ink supply tube and to apply a third force to a second valve element of the inkjet printer to urge the second valve element to open the communication path between the ink supply tube and the ink supply chamber when the ink cartridge is mounted to the inkjet printer. Moreover, a second urging member of the inkjet printer is configured to apply a fourth force to the second valve element to urge the second valve element to close the communication path between the ink supply tube and the ink supply chamber, and the third force is greater than the fourth force.