The curtal sonnet is a poetic form created by Gerard Manley Hopkins and used in three of his poems. It has eleven lines, or more accurately, ten-and-a-half lines. Unlike a standard sonnet, it follows the structure of a Petrarchan sonnet, but each section is three-quarters the length of its original form. This means the octave (first eight lines) of a Petrarchan sonnet becomes a sestet (six lines) in the curtal sonnet, and the sestet (last six lines) becomes a quatrain (four lines) plus an additional "tail piece" (a half line). The first eight lines of a standard sonnet are condensed into the first six lines of the curtal sonnet, and the last six lines are condensed into the final four-and-a-half lines. Hopkins described the last line as half a line, though it may be shorter than half of his usual sprung rhythm lines. In the preface to his Poems (1876–89), Hopkins explained the relationship between Petrarchan and curtal sonnets mathematically. If a Petrarchan sonnet is represented by the equation 8+6=14, the curtal sonnet is represented by 6+4.5=10.5.

Hopkins’s only examples of the form are "Pied Beauty," "Peace," and "Ash Boughs." "Pied Beauty" demonstrates the proportional relationship to the Petrarchan sonnet, as noted in the preface. Accents in the poem indicate stressed syllables.

Hopkins’s description of the form appears in the preface to his Poems (1876–89). Scholars agree that the curtal sonnet is not a new form but an interpretation of sonnet structure as Hopkins understood it. Elisabeth Schneider notes that the curtal sonnet reflects Hopkins’s focus on the mathematical proportions of sonnets. Lois Pitchford analyzes all three poems in detail, connecting them to the form as Hopkins imagined it.

The curtal sonnet has been used occasionally by other poets, often as a novelty, in contrast to Hopkins’s serious approach. Poets such as Lucy Newlyn and R. H. W. Dillard have written examples that explain the form.