A liquid supply unit configured to supply liquid and mountable to a liquid ejection device comprising a first liquid introducing part, a second liquid introducing part, a third liquid introducing part and a fourth liquid introducing part, the liquid supply unit comprising: a bottom wall comprising a first liquid supply section configured to be in contact with the first liquid introducing part, a second liquid supply section configured to be in contact with the second liquid introducing part, a third liquid supply section configured to be in contact with the third liquid introducing part and a fourth liquid supply section configured to be in contact with the fourth liquid introducing part; a top wall opposed to the bottom wall; a first end wall arranged to intersect with the bottom wall and the top wall and configured to have a first portion and a second portion; a second end wall arranged to intersect with the bottom wall and the top wall and to be opposed to the first end wall; and a) a contact part located on the second portion and allowed to be in electrically contact with the liquid ejection device, or b) an engagement part located on the second portion and configured to engage with an engagement arm, the engagement arm being configured to be rotated and displaced to be engaged with the liquid supply unit, characterized in that: a distance between the second end wall and the first portion is greater than a distance between the second end wall and the second portion in a plan view of the bottom wall in a first direction toward the bottom wall. a bottom wall comprising a first liquid supply section configured to be in contact with the first liquid introducing part, a second liquid supply section configured to be in contact with the second liquid introducing part, a third liquid supply section configured to be in contact with the third liquid introducing part and a fourth liquid supply section configured to be in contact with the fourth liquid introducing part; a top wall opposed to the bottom wall; a first end wall arranged to intersect with the bottom wall and the top wall and configured to have a first portion and a second portion; a second end wall arranged to intersect with the bottom wall and the top wall and to be opposed to the first end wall; and a) a contact part located on the second portion and allowed to be in electrically contact with the liquid ejection device, or b) an engagement part located on the second portion and configured to engage with an engagement arm, the engagement arm being configured to be rotated and displaced to be engaged with the liquid supply unit, a) a contact part located on the second portion and allowed to be in electrically contact with the liquid ejection device, or b) an engagement part located on the second portion and configured to engage with an engagement arm, the engagement arm being configured to be rotated and displaced to be engaged with the liquid supply unit, characterized in that: a distance between the second end wall and the first portion is greater than a distance between the second end wall and the second portion in a plan view of the bottom wall in a first direction toward the bottom wall.