If everything stays as it is, well... World War III hasn't started yet, but for now there are three direct conflicts:

USA + Israel vs. Iran.
It's a peripheral war (a major power is involved — that's clear), but still peripheral.

In the big picture, two major players are involved, but in different parts of the globe:

Russia vs. Ukraine

USA vs. Iran

It's not a world war yet, though we're on the edge — I'm holding back judgment.

This could take a long time. Here's a list of those involved:

Ukrainian War:

Russia (direct)
Ukraine (direct)
NATO (support)
USA (support)
China (support)
North Korea (support)

Iranian War:
Iran (direct)
Israel (direct)
United States (direct)

Speculative:

Taiwan War:
China (direct)
Taiwan (direct)
USA (support)
WWIII (Hypothetical lineup):
USA
NATO
Israel
vs
Russia
China
North Korea
Iran