Triarius was a Gothic nobleman and soldier.

Triarius may also refer to:

• Triarius (tree), an 86.5-metre-high Eucalyptus regnans (swamp gum tree) in Tasmania
• Triarius (beetle) is a genus of skeletonizing leaf beetles in the family Chrysomelidae
• Triarii, elements of early Roman military legions, consisting of wealthy and older men

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