The perfect tense or aspect (abbreviated PERF or PRF) is a verb form that indicates that an action or circumstance occurred earlier than the time under consideration, often focusing attention on the resulting state rather than on the occurrence itself. An example of a perfect construction is I have made dinner. Although this gives information about a prior action (the speaker's making of the dinner), the focus is likely to be on the present consequences of that action (the fact that the dinner is now ready). The word perfect in this sense means "completed" (from Latin perfectum, which is the perfect passive participle of the verb perficere "to complete").

In traditional Latin and Ancient Greek grammar, the perfect tense is a particular, conjugated-verb form. Modern analyses view the perfect constructions of these languages as combining elements of grammatical tense (such as time reference) and grammatical aspect. The Greek perfect tense is contrasted with the aorist and the imperfect tenses and specifically refers to completed events with present consequences; its meaning is thus similar to that of the English construction, "have/has (done something)". The Latin perfect tense is contrasted only with the imperfect tense (used for past incomplete actions or states) and is thus used to mean both "have/has done something" and "did something" (the preterite use). Other related forms are the pluperfect, denoting an event prior to a past time of reference, and the future perfect, for an event prior to a future time of reference.

In the grammar of some modern languages, particularly of English, the perfect may be analyzed as an aspect that is independent of tense – the form that is traditionally just called the perfect ("I have done") is then called the present perfect, while the form traditionally called the pluperfect ("I had done") is called the past perfect. (There are also additional forms such as future perfect, conditional perfect, and so on.) The formation of the perfect in English, using forms of an auxiliary verb (have) together with the past participle of the main verb, is paralleled in a number of other modern European languages.

The perfect can be denoted by the glossing abbreviation PERF or PRF. It should not be confused with the perfective aspect (PFV), which refers to the viewing of an action as a single (but not necessarily prior) event. To avoid confusion with the perfective, the perfect is occasionally called the retrospective (RET).

In some analyses, the perfect is identified as one of the grammatical aspects. In the perfect aspect, the event being referred to is viewed as already completed at the time of reference. It should not be confused with the perfective aspect, which marks a situation as a single event without internal structure, and does not imply prior occurrence or present relevance as the perfect aspect does. The perfect also contrasts with the prospective aspect, which encodes the present relevance or anticipation of a future event. While the perfect is a relatively uniform category cross-linguistically, its relation to the experiential and resultative aspects is complex – the latter two are not simply restricted cases of the perfect.

The perfect is not necessarily incompatible with other grammatical aspects. In English, for example, it can be combined with the progressive (continuous) aspect, wherein an event is viewed as temporary and ongoing. A form such as the present perfect progressive I have been working combines the meanings expressed by the two aspects – viewing my working as an ongoing process, but one which is now completed (or, as in I have been working for two hours, restricting attention to the completed portion of that process).

If perfect is viewed as an aspect, then the verb forms traditionally called just "perfect" (as in Greek or – in appropriate contexts – in Latin) in fact combine the perfect aspect with present tense (the event occurred prior to the time of speech). The pluperfect and future perfect forms combine perfect aspect with past and future tense respectively. This analysis is reflected more explicitly in the terminology commonly used in modern English grammars, which refer to present perfect, past perfect and future perfect (as well as some other constructions such as conditional perfect).

However, not all uses of "perfect" verb forms necessarily express this "perfect aspect" – sometimes they are simply used as expressions of past tense, that is, as preterites. This applies to some uses of the Latin perfect, and also (for example) to the modern German Perfekt.