The English language has many irregular verbs, approaching 200 in normal use—and significantly more if prefixed forms are counted. In most cases, the irregularity concerns the past tense (also called preterite) or the past participle.

The other inflected parts of the verb—the third person singular present indicative in -[e]s, and the present participle and gerund form in -ing—are formed regularly in most cases. There are a few exceptions: the verb be has irregular forms throughout the present tense; the verbs have, do, and say have irregular -[e]s forms; and certain defective verbs (such as the modal auxiliaries) lack most inflection.

The irregular verbs include many of the most common verbs: the dozen most frequently used English verbs are all irregular. New verbs (including loans from other languages, and nouns employed as verbs) usually follow the regular inflection, unless they are compound formations from an existing irregular verb (such as housesit, from sit).

Irregular verbs in Modern English are typically derived from verbs that followed more regular patterns at a previous stage in the history of the language. In particular, many such verbs derive from Germanic strong verbs, which make many of their inflected forms through vowel gradation, as can be observed in Modern English patterns such as sing–sang–sung. The regular verbs, on the other hand, with their preterites and past participles ending in -ed, follow the weak conjugation, which originally involved adding a dental consonant (-t or -d). Nonetheless, there are also many irregular verbs that follow or partially follow the weak conjugation.

For information on the conjugation of regular verbs in English, as well as other points concerning verb usage, see English verbs.