Siona (otherwise known as Bain Coca, Pioje, Pioche-Sioni, Ganteyabain, Ganteya, Ceona, Zeona, Koka, Kanú) is a Tucanoan language of Colombia and Ecuador.

Ecuadorian Siona and Colombian Siona, as well as Secoya, have a high level of mutual intelligibility, but have some lexical, morphological, and phonological differences between them.

Both often produce a noticeable delay before the onset of the following vowel: the 'fortis' series (written p t č k kw s h hw) tends to be aspirated, with a noisy transition to the vowel, while the 'lenis' series (written b d g gw ’ z), optionally voiced, is glottalized, with a silent transition to the vowel, which in turn tends to be laryngealized.

The glottal stop is faint, and noticeable primarily in the laryngealizing effect it has on adjacent vowels.

Stress is obligatory on all verb stems, root words, and some suffixes.