By the time he began Astrophil and Stella, most likely during the latter part of 1581, Sidney had already experimented extensively with different variations upon the sonnet form, both in the Old Arcadia and the Certain Sonnets collection. The word ‘sonnet’, from Italian sonneto ('little sound’), is generally understood to denote a fourteen-line or ‘quatorzain’ lyric poem, though there are many contemporary examples that deploy more than fourteen lines, including nineteen of the Certain Sonnets. Comprising 108 quatorzain sonnets and eleven songs of varying length and metre Sidney's sequence charts the suit of a virtuous married woman Stella ('star’) by the young, self-conscious, increasingly obsessive courtier Astrophil ('star-lover’). It adopts essentially the same narrative arc found in Sidney's Philisides-Mira poems, though Astrophil is far more physical and sexual than Philisides.

In the first, unauthorized edition of Astrophil, published by Thomas Newman in 1591, the preface by Nashe promised the reader a ‘Theater of pleasure’ and sketched out the tragic shape of Astrophil's story:

The first sixty or so sonnets find Astrophil engaged in a seemingly fruitless adoration and pursuit of his beloved, but then in a sequence from Sonnets 61-72 Stella offers a guarded declaration of her love for Astrophil, a chaste love that will uphold her virtue: