A lipid composition comprising: a first lipid which is a lipid represented by Formula or a salt thereof; sterols; and nucleic acid, wherein a ratio of the number of moles of the first lipid in the lipid composition to the number of moles of the sterols in the lipid composition is 0.300 or more and less than 1.299, in the formula, X represents -NR 1 - or -O-, R 1 represents a hydrogen atom, a hydrocarbon group having 6 to 24 carbon atoms, or a group represented by R 21 -L 1 -R 22 -, where R 21 represents a hydrocarbon group having 1 to 24 carbon atoms, L 1 represents -O O-, -O -, - O-, -O-, or a group represented by the following formula,, and R 22 represents a divalent hydrocarbon linking group having 1 to 18 carbon atoms, R 2 and R 3 each independently represent a hydrogen atom, a hydrocarbon group having 3 to 24 carbon atoms, or a group represented by R 31 -L 2 -R 32 -, where R 31 represents a hydrocarbon group having 1 to 24 carbon atoms, L 2 represents -O O-, -O -, - O-, -O-, or a group represented by the following formula,, and R 32 represents a divalent hydrocarbon linking group having 1 to 18 carbon atoms, R 4, R 5, R 6, R 7, R 8, R 9, R 10, R 11, and R 12 each independently represent a hydrogen atom or an alkyl group having 1 to 18 carbon atoms which may be substituted, groups in any one or more pairs among R 4 and R 5, R 10 and R 5, R 5 and R 12, R 4 and R 6, R 5 and R 6, R 6 and R 7, R 6 and R 10, R 12 and R 7, and R 7 and R 8 may be linked to each other to form a 4- to 7-membered ring which may contain an O atom, a substituent on the alkyl group having 1 to 18 carbon atoms which may be substituted is a hydroxyl group, a carboxyl group, an amino group represented by -NR 45 R 46, a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, or a group represented by -O O-R 41, -O -R 42, - O-R 43, or -O-R 44, where R 41, R 42, R 43, R 44, R 45, and R 46 each independently represent a hydrocarbon group having 1 to 18 carbon atoms, a substituent on the substituted or unsubstituted aryl group and on the substituted or unsubstituted heteroaryl group is an alkyl group having 1 to 18 carbon atoms, a hydroxyl group, a carboxyl group, an amino group represented by -NR 45 R 46, or a group represented by -O O-R 41, -O -R 42, - O-R 43, or -O-R 44, where R 41, R 42, R 43, R 44, R 45, and R 46 each independently represent a hydrocarbon group having 1 to 18 carbon atoms, and a, b, c, and d each independently represent an integer of 0 to 3, a + b is 1 or more, and c + d is 1 or more. a first lipid which is a lipid represented by Formula or a salt thereof; sterols; and nucleic acid, wherein a ratio of the number of moles of the first lipid in the lipid composition to the number of moles of the sterols in the lipid composition is 0.300 or more and less than 1.299, in the formula, X represents -NR 1 - or -O-, R 1 represents a hydrogen atom, a hydrocarbon group having 6 to 24 carbon atoms, or a group represented by R 21 -L 1 -R 22 -, where R 21 represents a hydrocarbon group having 1 to 24 carbon atoms, L 1 represents -O O-, -O -, - O-, -O-, or a group represented by the following formula,, and R 22 represents a divalent hydrocarbon linking group having 1 to 18 carbon atoms, R 2 and R 3 each independently represent a hydrogen atom, a hydrocarbon group having 3 to 24 carbon atoms, or a group represented by R 31 -L 2 -R 32 -, where R 31 represents a hydrocarbon group having 1 to 24 carbon atoms, L 2 represents -O O-, -O -, - O-, -O-, or a group represented by the following formula,, and R 32 represents a divalent hydrocarbon linking group having 1 to 18 carbon atoms, R 4, R 5, R 6, R 7, R 8, R 9, R 10, R 11, and R 12 each independently represent a hydrogen atom or an alkyl group having 1 to 18 carbon atoms which may be substituted, groups in any one or more pairs among R 4 and R 5, R 10 and R 5, R 5 and R 12, R 4 and R 6, R 5 and R 6, R 6 and R 7, R 6 and R 10, R 12 and R 7, and R 7 and R 8 may be linked to each other to form a 4- to 7-membered ring which may contain an O atom, a substituent on the alkyl group having 1 to 18 carbon atoms which may be substituted is a hydroxyl group, a carboxyl group, an amino group represented by -NR 45 R 46, a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, or a group represented by -O O-R 41, -O -R 42, - O-R 43, or -O-R 44, where R 41, R 42, R 43, R 44, R 45, and R 46 each independently represent a hydrocarbon group having 1 to 18 carbon atoms, a substituent on the substituted or unsubstituted aryl group and on the substituted or unsubstituted heteroaryl group is an alkyl group having 1 to 18 carbon atoms, a hydroxyl group, a carboxyl group, an amino group represented by -NR 45 R 46, or a group represented by -O O-R 41, -O -R 42, - O-R 43, or -O-R 44, where R 41, R 42, R 43, R 44, R 45, and R 46 each independently represent a hydrocarbon group having 1 to 18 carbon atoms, and a, b, c, and d each independently represent an integer of 0 to 3, a + b is 1 or more, and c + d is 1 or more.