In grammar, a content clause is a dependent clause that provides content implied or commented upon by an independent clause. The term was coined by Danish linguist Otto Jespersen. Content clauses have also traditionally been called noun clauses or nominal clauses, but current linguistics tends to view those names as misnomers and prefers content clause.

In English, there are two main kinds of content clauses: declarative content clauses (or that-clauses), which correspond to declarative sentences, and interrogative content clauses, which correspond to interrogative sentences.

Declarative content clauses can have a number of different grammatical roles. They often serve as direct objects of verbs of reporting, cognition, perception, and so on. In this use, the conjunction that may head the clause, but is often omitted:

Similarly with certain verb-like adjectives:

They also often serve as complements of nouns—both nouns corresponding to the above verbs, and nouns like fact, idea, and so on. Here, that is almost always included:

Finally, they can serve as subjects, as complements of predicative adjectives in clauses with linking verbs or in small clauses or as object complements. In this latter use, they are commonly postponed to the end of their main clause, with an expletive it standing in their original place as subject:

Here as before, a conjunction is almost always included, although it does not need to be that:

Interrogative content clauses, often called indirect questions, can be used in many of the same ways as declarative ones; for example, they are often direct objects of verbs of cognition, reporting, and perception, but here they emphasize knowledge or lack of knowledge of one element of a fact: