Liliopsida is a botanical name for the class containing the family Liliaceae (or Lily Family). It is considered synonymous (or nearly synonymous) with the name monocotyledon. Publication of the name is credited to Scopoli (in 1760): see author citation (botany). This name is formed by replacing the termination -aceae in the name Liliaceae by the termination -opsida (Art 16 of the ICBN).

Although in principle it is true that circumscription of this class will vary with the taxonomic system being used, in practice this name is very strongly linked to the Cronquist system, and the allied Takhtajan system. These two are the only major systems to use the name, and in both these systems it refers to the group more widely known as the monocotyledons. Earlier systems referred to this group by the name Monocotyledones, with Monocotyledoneae an earlier spelling (these names may be used in any rank). Systems such as the Dahlgren and Thorne systems (more recent than the Takhtajan and Cronquist systems) refer to this group by the name Liliidae (a name in the rank of subclass). Modern systems, such as the APG and APG II systems refer to this group by the name monocots (a name for a clade). Therefore in practice the name Liliopsida will almost surely refer to the usage as in the Cronquist system.

In summary the monocotyledons were named:

• Monocotyledoneae in the de Candolle system and the Engler system.
• Monocotyledones in the Bentham & Hooker system and the Wettstein system
• class Liliopsida in the Takhtajan and the Cronquist system (also in the Reveal system).
• subclass Liliidae in the Dahlgren system and the Thorne system (1992).
• clade monocots in the APG system and the APG II system.

Each of the systems mentioned above use their own internal taxonomy for the group.