In ancient Celtic religion, Ialonus Contrebis or Ialonus or Gontrebis was a god (or perhaps two related gods) worshipped in what are now Lancashire and Provence. He is known from three dedicatory inscriptions. One, at Lancaster, was dedicated (in the dative) to Deo Ialono Contre Sanctissimo ("to the holiest god Ialonus Contre[bis]"); another, at Overborough in Kirkby Lonsdale, to Deo San Gontrebi ("to the holy god Gontrebis"). In the third inscription, found at Nîmes in Provence, Ialonus was invoked in conjunction with the goddess Fortune.
The name Contrebis may possibly contain a root related to Proto-Celtictrebo- 'house'. That of Ialonus may be related to the Proto-Celtic root jalo- 'clearing'.