The Doctrine of the Trinity Act 1813 (sometimes called the Trinitarian Act 1812) was an Act of the Parliament of the United Kingdom. It amended the Blasphemy Act 1697 in respect of its Trinitarian provisions.

The Act, passed in 21 July 1813, granted toleration for Unitarian worship, as previously the Act of Toleration 1689 had only granted toleration to those Protestant dissenters who accepted the Trinity.

As a result all forms of worship were now tolerated.