In Jainism it is difficult to point to one single “oldest temple in the world” because:

• Jain Dharma is extremely ancient.
• The very early shrines were mostly simple or rock‑cut caves, not big stone temples with shikhars.
• Many early structures have been destroyed or rebuilt several times.

Still, from what historians and Jain traditions generally accept today, we can say:

1. Oldest Jain religious site (cave type, not a built temple)

- The Udaygiri–Khandagiri caves near Bhubaneswar (Odisha, India) were made around 2nd century BCE. - These were rock‑cut caves prepared specially for Jain monks to live, meditate and do spiritual practices. - They are among the oldest surviving Jain religious structures in the world, but technically they are caves/monastic cells, not a temple with a garbhagriha and shikhar.

1. Among the oldest surviving standing Jain temples

- The Mahavira Jain Temple at Osian (near Jodhpur, Rajasthan) is usually counted as one of the oldest still‑standing Jain temples (structural temple), dated around the 8th century CE. - It is very important for the Oswal Jain community and is often mentioned as the oldest surviving Jain temple of Western India.

So:

• If you mean any Jain religious place, then cave complexes like Udaygiri–Khandagiri are among the oldest.
• If you mean a proper standing temple building, then Mahavira Jain Temple, Osian is usually given as one of the oldest surviving Jain temples.

Because of lost history and rebuilding, no scholar can say with 100% certainty “this is the single oldest Jain temple in the whole world,” but all the very ancient ones are in India.