An ink cartridge (30, 30A, 30B, 30D,) for installing in a cartridge mounting portion of a recording apparatus, comprising in an orientation in which it is intended to be used: a body (31, 31A, 31B, 31D) having a front side at which an ink supply portion is located for supplying ink stored in an ink chamber to an exterior of the ink chamber, a rear side located to face the front side, an upper surface and a bottom surface opposite to the upper surface, the upper surface extending from a front surface positioned at the front side to a rear surface positioned at the rear side, and wherein the ink cartridge is provided with an engagement portion (90, 44D) comprising a first guide surface and a second guide surface; a particular interface positioned substantially adjacent to the ink supply portion at the front side, wherein the particular interface is configured to be biased by a biasing member (139, 839) in a specific direction; and the engagement portion (90, 44D) configured to be engaged with a locking section (108, 109) of a cartridge installation portion for retaining the body (31, 31A, 31B, 31D) in an installed state from moving in the specific direction against a biasing force of the biasing member, characterized in that the bottom surface is provided with the engagement portion (90, 44D); the engagement portion (90, 44D) is resiliently deformable in a manner to be resiliently deformed when the ink cartridge (30, 30A, 30B, 30D) is installed in the cartridge mounting portion; and the first guide surface and the bottom surface define a first angle (θ1) therebetween and the second guide surface and the bottom surface define a second angle (θ2) therebetween greater than the first angle (θ1). a body (31, 31A, 31B, 31D) having a front side at which an ink supply portion is located for supplying ink stored in an ink chamber to an exterior of the ink chamber, a rear side located to face the front side, an upper surface and a bottom surface opposite to the upper surface, the upper surface extending from a front surface positioned at the front side to a rear surface positioned at the rear side, and wherein the ink cartridge is provided with an engagement portion (90, 44D) comprising a first guide surface and a second guide surface; a particular interface positioned substantially adjacent to the ink supply portion at the front side, wherein the particular interface is configured to be biased by a biasing member (139, 839) in a specific direction; and the engagement portion (90, 44D) configured to be engaged with a locking section (108, 109) of a cartridge installation portion for retaining the body (31, 31A, 31B, 31D) in an installed state from moving in the specific direction against a biasing force of the biasing member, the bottom surface is provided with the engagement portion (90, 44D); the engagement portion (90, 44D) is resiliently deformable in a manner to be resiliently deformed when the ink cartridge (30, 30A, 30B, 30D) is installed in the cartridge mounting portion; and the first guide surface and the bottom surface define a first angle (θ1) therebetween and the second guide surface and the bottom surface define a second angle (θ2) therebetween greater than the first angle (θ1).