  The main aim of this article is to study and develop valuation theory for
Krasner hyperfields. In analogy with classical valuation theory for fields, we
generalise the formalism of valuation rings to describe equivalence of
valuations on hyperfields. After proving basic results and discussing several
examples, we focus on the valued hyperfields that Krasner originally defined in
1957. We find that these must have a particular additive structure which in
turns implies the existence of a valuation a'la Krasner. We note that given
such a valued hyperfield $(F,v)$, the valuation induced by its additive
structure does not have to be equivalent to $v$. We discuss the cases in which
it does.
