  We construct the 12-dimensional exceptional field theory associated to the
group $\mathrm{SL}(2) \times \mathbb{R}^+$ . Demanding the closure of the
algebra of local symmetries leads to a constraint, known as the section
condition, that must be imposed on all fields. This constraint has two
inequivalent solutions, one giving rise to 11-dimensional supergravity and the
other leading to F-theory. Thus $\mathrm{SL}(2) \times \mathbb{R}^+$
exceptional field theory contains both F-theory and M-theory in a single
12-dimensional formalism.
