A further improvement in convenience is desired in conventional liquid ejecting systems. A liquid supplying unit is mountable to a carriage that has a first projection, a second projection and a liquid introduction needle. The liquid supplying unit includes: a first wall portion; a second wall portion opposing the first wall portion; a third wall portion intersecting the first wall portion and the second wall portion; a fourth wall portion opposing the third wall portion; a fifth wall portion intersecting the first wall portion, the second wall portion, the third wall portion and the fourth wall portion; and a sixth wall portion opposing the fifth wall portion. The first wall portion is provided with a liquid supplying portion connectable to a liquid introduction needle, a first recess portion into which the first projection can be inserted, and a second recess portion into which the second projection can be inserted. In a planar view of the first wall portion, the liquid supplying portion is positioned closer to the fifth wall portion than to the sixth wall portion, and when the first wall portion is equally divided into a first region, a second region and a third region, the first recess portion is positioned in the first region, and the second recess portion is positioned in the third region.