In linguistics, quirky subjects (also called oblique subjects) are a phenomenon where certain verbs specify that their subjects are to be in a case other than the nominative. These non-nominative subjects are determiner phrases that pass subjecthood tests such as subject-oriented anaphora binding, PRO control, reduced relative clause, conjunction reduction, subject-to-subject raising, and subject-to-object raising.

It has been observed cross-linguistically that the subject of a sentence often has a nominative case. However, this one-to-one relationship between case and grammatical relations (subjecthood) is highly debatable. Some argue that nominative case marking and controlling verb agreement are not unique properties of subjects. One evidence in support of this proposal is the observation that nominative can also mark left-dislocated NPs, appellatives and some objects in the active in Icelandic. In addition, agreeing predicate NPs can also be marked nominative case:

In Standard English, a sentence like "*Me like him" is ungrammatical because the subject is ordinarily in the nominative case. In many or most nominative–accusative languages, this rule is inflexible: the subject is indeed in the nominative case, and almost all treat the subjects of all verbs the same. Icelandic was argued to be the only modern language with quirky subjects, but other studies investigating languages like Faroese, German, Hindi, Basque, Laz, Gujarati, Hungarian, Kannada, Korean, Malayalam, Marathi, Russian, Spanish, and Telugu show that they also possess quirky subjects.

The class of quirky subjects in Icelandic is a large one, consisting of hundreds of verbs in a number of distinct classes: experiencer verbs like vanta (need/lack), motion verbs like reka (drift), change of state verbs like ysta (curdle), verbs of success/failure like takast (succeed/manage to), verbs of acquisition like áskotnast (acquire/get by luck), and many others.

In superficially similar constructions of the type seen in Spanish me gusta "I like", the analogous part of speech (in this case me) is not a true syntactical subject. "Me" is instead the object of the verb "gusta" which has a meaning closer to "please", thus, "me gusta" could be translated as "(he/she/it) pleases me" or "I am pleased by [x]."

Many linguists, especially from various persuasions of the broad school of cognitive linguistics, do not use the term "quirky subjects" since the term is biased towards languages of nominative–accusative type. Often, "quirky subjects" are semantically motivated by the predicates of their clauses. Dative-subjects, for example, quite often correspond with predicates indicating sensory, cognitive, or experiential states across a large number of languages. In some cases, this can be seen as evidence for the influence of active–stative typology.