Liliidae is a botanical name at the rank of subclass.^[1] Circumscription of the subclass will vary with the taxonomic system being used (there are many such systems); the only requirement being that it includes the family Liliaceae.

The Takhtajan system treats this as one of six subclasses within class Liliopsida (= monocotyledons). This subclass consists of:

• subclass Liliidae

  superorder Lilianae

  order Melanthiales

  order Colchicales

  order Trilliales

  order Liliales

  order Alstroemeriales

  order Iridales

  order Tecophilaeales

  order Burmanniales

  order Hypoxidales

  order Orchidales

  order Amaryllidales

  order Asparagales

  order Xanthorrhoeales

  order Hanguanales

  superorder Dioscoreanae

  order Stemonales

  order Smilacales

  order Dioscoreales

  order Taccales

The Cronquist system treats this as one of five subclasses within class Liliopsida (= monocotyledons), and it consists of:

• subclass Liliidae

  order Liliales

  order Orchidales

In the Dahlgren system and the Thorne system (1992) this is an important name: this subclass comprises the monocotyledons (in APG II these are the monocots).

The APG and APG II systems do not use formal botanical names above the rank of order, and names such as Liliopsida and Liliidae have no place in these systems.