A play titled Titirus and Galathea was entered into the Stationers' Register on 1 April 1585. Some scholars have speculated that this play, otherwise unknown, may have been an early version of Lyly's work — though the point is open to doubt, since what clearly was Lyly's play was entered into the Register on 4 October 1591, along with his Endymion and Midas. Gallathea was acted at the royal palace at Greenwich before Queen Elizabeth I by the Children of Paul's, most likely on 1 January 1588 (new style). Gallathea was first printed in 1592, in a quarto printed by John Charlwood for Joan Broome (the widow of bookseller William Broome, who had published reprints of Lyly's Campaspe and Sapho and Phao in 1591). Gallathea was next printed in Six Court Comedies (1632), the first collected edition of Lyly's works.
A small village somewhere in Lincolnshire is forced by Neptune to sacrifice their most beautiful virgin to him every five years, or he will drown them all. The chosen virgin must be tied to a certain tree to await her fate at the hands of the Agar, a terrible monster. The fathers (Tyterus and Melebus) of the two most beautiful virgins of the village, Gallathea and Phillida, decide to disguise their daughters as boys until after the sacrifice. Both girls are then sent off into the woods. Meanwhile, in an almost completely unrelated subplot, three brothers, Rafe, Robin, and Dick, set off to seek their fortune. At the same time, the god Cupid is wandering through the forest when he happens upon a nymph of Diana. After a rebuff of his amorous advances, he resolves to trick all of the nymphs into falling in love, despite their vows of chastity. Predictably, all three of the nymphs who appear fall in love with either Gallathea or Phillida, whom Diana has forced to assist in her hunt. The rest of the plot revolves around the relationship between Gallathea and Phillida, who, each believing the other to be a boy, fall in love with each other. Cupid's punishment, substitute sacrifices of inferior virgins, brotherly reunions, divine reconciliations, a surprise ending, and the triumph of true love ensue.
The play follows three plots that pass through five stages with which being intertwined. In Act 1, arriving in a wooden island, the fathers, Tyterus and Melebus, discuss their plan to disguise their daughters and hide them in the woods. In Act 2, the deception fall amongst the characters in which each one is deceiving another and another. Act 3 continues on with the deception and woes by the characters with no resolution. By Act 4, the deception and confusion has peaked to a climax and thus begins to fall down towards a resolution of the plot. Act 5 reveals the resolution and rejoicing of the play and characters.
- Tityrus, a shepherd
- Gallatea, his daughter, disguised as Tyterus II
- Melebeus, a shepherd
- Phillida, his daughter, disguised as Melebuss II
- Venus, goddess of love
- Neptune, god of the sea
- Diana, goddess of virginity and of the hunt
Nymphs of Diana (4)
- another Nymph of Diana
- Ericthinis, a citizen
- Hebe, his virgin daughter
Three servant-brothers, cast ashore in a shipwreck
- Peter, servant to an Alchemist
One of the first recorded productions in the 20th Century was directed by Ivan Fuller at Augustana College in Sioux Falls, SD in 1998. The production sparked a 2003 paper "Everything Old is New Again: The Elizabethan and the Contemporary Appeal in Lyly’s Gallathea" which was presented at the Shakespeare Association of America Conference, Victoria, BC.
A production directed by Brett Sullivan Santry, was performed by the students of Stuart Hall School of Staunton, Virginia. When he directed the play, he was an MLitt/MFA graduate student in Shakespeare and Renaissance Literature in Performance at Mary Baldwin College. It ran from 2 to 5 February 2007.  The production also appeared among the calendar of featured events, during the week-long celebration of Shakespeare's birthday, at the American Shakespeare Center's Blackfriars Playhouse on 17 April 2007. 
Quest Theater Ensemble, Astoria, Queens (2002). Adapted and directed by Tim Browning. Music composed by jazz guitarist Spiros Exaras.
Modern commentators have praised the play's "harmonious variety" and "allegorical dramaturgy."
- E. K. Chambers, The Elizabethan Stage, 4 Volumes, Oxford, Clarendon Press, 1923; Vol. 2, p. 18.
- Chambers, Vol. 3, pp. 413, 415.
- Anastasia Zhuravleva. "Gallathea is in a relationship and it's complicated." The California Aggie. 4 November 2010. 
- Terence P. Logan and Denzell S. Smith, eds., The Predecessors of Shakespeare: A Survey and Bibliography of Recent Studies in English Renaissance Drama, Lincoln, NE, University of Nebraska Press, 1973; pp. 134-5.
- Gallathea: full text in the English Prose Drama Full-Text Database (EProseD) at Indiana University.