Fuente: WIPO "tomato" The present invention provides: a neutral lipid capable of suppressing the phase transition of endosomal membranes caused by phosphatidylcholine from being inhibited; and a lipid nanoparticle containing the neutral lipid. The present invention pertains to an ionic neutral lipid comprising a compound represented by general formula (I). [In formula (I), R1 is a C1-22 hydrocarbon group; three R1 groups in one molecule may be the same as or different from each other; a1 and a2 are each independently an integer of 0 to 4; b1 and b2 are 0 or 1, satisfying b1+b2=1; R2 and R3 are each independently a hydrogen atom or a C1-3 alkyl group; and R4 is an anionic group.]