LIPID COMPOSITION

An object of the present invention is to provide a lipid composition capable of achieving excellent nucleic acid delivery for a wide variety of nucleic acids. According to the present invention, there is provided a lipid composition containing a first lipid which is a lipid represented by Formula (1) or a salt thereof, sterols, and nucleic acid, in which a ratio of the number of moles of the first lipid in the lipid composition to the number of moles of sterols in the lipid composition is 0.300 or more and less than 1.299.In the formula, X represents -NR1- or -O-, R1 represents a hydrogen atom, a hydrocarbon group, or the like, R2 and R3 each independently represent a hydrogen atom, a hydrocarbon group, or the like, R4, R5, R6, R7, R8, R9, R10, R11, and R12 each independently represent a hydrogen atom or an alkyl group,groups in any one or more pairs among R4 and R5, R10 and R5, R5 and R12, R4 and R6, R5 and R6, R6 and R7, R6 and R10, R12 and R7, and R7 and R8 may be linked to each other to form a 4- to 7-membered ring which may contain an O atom, a, b, c, and d are each independently represent an integer of 0 to 3, a + b is 1 or more, and c + d is 1 or more.