MJO is the Madden–Julian oscillation, the largest element of the intraseasonal variability in the tropical atmosphere.

MJO may also refer to:

• ISO 639:mjo, the ISO 639 code for the Malankuravan language
• Mount Etjo Airport, the IATA code MJO
• Metropolitan Jazz Octet, a group created by Chicago saxophonist and arranger Tom Hilliard

• M JO, a fashion label created by Taiwanese singer and actor Jiro Wang

This disambiguation page lists articles associated with the title MJO.
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