In this article, we introduce and study a new class of operators defined on a Cartesian product of ideal spaces of measurable functions. We use the general approach of the theory of vector lattices. We say that an operator
T
:
E
×
F
⟶
W
defined on a Cartesian product of vector lattices
E
and
F
and taking values in a vector lattice
W
is orthogonally biadditive if all partial operators
T
y
:
E
⟶
W
and
T
x
:
F
⟶
W
are orthogonally additive. In the first part of the article, we prove that, under some mild conditions, a vector space of all regular orthogonally biadditive operators
O
B
A
r
E
,
F
;
W
is a Dedekind complete vector lattice. We show that the set of all horizontally-to-order continuous regular orthogonally biadditive operators is a projection band in
O
B
A
r
E
,
F
;
W
. In the last section of the paper, we investigate orthogonally biadditive operators on a Cartesian product of ideal spaces of measurable functions. We show that an integral Uryson operator which depends on two functional variables is orthogonally biadditive and obtain a criterion of the regularity of an orthogonally biadditive Uryson operator.