This study describes the verse design of Old English poetry in terms of modern phonological theory, developing an analysis which allows all OE verse lines to be described in terms of single metrical design. Old English poetry is typified by a single type of line of variable length, characterised by four metrical peaks. The variation evident in the lengths of OE metrical units has caused previous models to overgenerate acceptable verse forms or to develop complex typologies of dozens of acceptable forms. In this study, Metrical phonology and Optimality theory are used to highlight some aspects of the relationship between syntax, phonology and verse metrics in determining how sentences and phrases interact with the verse structure to create variation. The main part of the study is a metrical model based on the results of a corpus analysis. The corpus is centred on the OE poems Genesis and Andreas, complemented by selected shorter poems. A template of a prototypical line is described based on a verse foot which contains three vocalic moras, and which can vary between 2 and 4 vocalic moras distributed across 1 to 4 syllables. Each standard line is shown to consist of four of these verse feet, leading to a line length which can vary between 8 and 16 vocalic moras. It is shown that the limited variation within the length of the verse foot causes the greater variation in the length of lines. The rare, longer ‘hypermetric’ line is also accounted for with a modified analysis. The study disentangles the verse foot, which is an abstract metrical structure, from the prosodic word, which is a phonological object upon which the verse foot is based, and with which it is often congruent. Separate sets of constraints are elaborated for creating prosodic words in OE, and for fitting them into verse feet and lines. The metrical model developed as a result of this analysis is supported by three smaller focused studies. The constraints for creating prosodic words are defended with reference to compounds and derivational nouns, and are supported by a smaller study focusing on the metrical realisation of non-Germanic personal names in OE verse. Names of biblical origin are often longer than the OE prosodic word can accommodate. The supporting study on non-Germanic names demonstrates how long words with no obvious internal morphology in OE are adapted first to OE prosody and then to the verse structure. The solution for the metrical realisation of these names is shown to be patterned on derivational nouns. The supporting study on compound numerals describes how phrases longer than a verse are accommodated by the verse design. It is shown that compound numerals, which consist of two or more numeral words (e.g. 777 – seofonhund and seofon and hundseofontig) are habitually rearranged within the text to meet the requirements of verse length and alliteration. A further supporting study discusses the difference between the line length constraints controlling OE verse design and those for Old Norse and Old Saxon verse. Previous studies have often conflated these three closely related traditions into a single system. It is shown that despite their common characteristics, the verse design described in this study applies to all OE verse, but not to ON or OS.