Hi, my name is Riccardo. I loved Pantheon since I first discovered him and started to play him as support when he was viable. When I switched to jungle I was so sad I couldn't play him, until in 12.10 they buffed him and into 12.14 they brought him back to jungle.
Since then I love to play him jungle because of his omnipresent playstyle, I was so sad that no one had an updated jungle guide for him, so I decided to make one.

Just a note, I'm not that much qualified for a guide. I play LoL since season 6, first mid, then support, and since season 11 as jungler.
My peak is Gold 2, not that much, but I follow a lot of Master/Challenger streamers and I stay informed on builds using sites like LoLAlytics, so the knowledge in this guides comes from there and not only from my experiences on SoloQ.

This guide will include only the actual playstyle I use and stay updated on, jungle Bruiser. I will not include jungle Duskblade Lethality builds as I don't like them on Pantheon in the current meta and I don't think they are viable. I'd prefere building him Sunfire if it were a thing.

All of the choices are explained on the notes, so be sure to read them all, the explanation will stay only there as it's easier to update.

I will not include notions on jungling or on general Pantheon abilities and combo. If you want a jungle guide there are a lot out there, but if you want a Pantheon guide with combo and abilities explained i suggest you this guide by Dustyacer (bear in mind that is for Laner Pantheon)

Abilities

Pantheon - The Unbreakable Spear Melee, DPS, Bruiser Why Pantheon Jungle? Lane Pantheon has the weakness of being very bad before hitting level 3 and having an R that is useless in lane dueling, making him useful only on certain matchups. Meanwhile support Pantheon is very bad all around in the meta actually. In jungle Pantheon can safely hit lvl 3 (his bigger early spike) in a short time and have the tools for early ganks and invades with his Shield Vault. At level 6 he has Grand Starfall that makes his ganks top tier, making him an excellent jungler. His Shield Vault is good for taking Rift scuttler, and Comet Spear with Mortal Will max stacks can make only a few champs outsmite your objectives and setup goods objective steals.

PROS + Huge gank potential and map presence + Strong early game + Easy outsmite most enemies + Has hard CC + Easy to learn + Good 2vs2 or 3vs3

CONS - Weak late game - Low utility when behind - Below average dueling - Aegis Assault can be easily negated with mobility

Pantheon's first clear is not so fast, so you usually want to early invade with your allies, try to catch an offposition enemy or doing a fast lvl 3 and right after early gank a lane into rift scuttler or invade the enemy jungler if no lane is in a gankable spot.
So your paths can be:

Red start:
➔ ➔ ➔ Gank/Invade ➔

Blue start:
➔ ➔ ➔ Gank/Invade ➔

Then you can think of doing a gank to midlane and follow up with the other rift scuttler into clearing the other side of your jungle and recall or recall right after if you have at least money for a Serrated Dirk / Ironspike Whip, otherwise opt for a second jungle clear if you are not low and at risk of an invade

Choose if you're starting Red or Blue based on comps and which lane is more likely to be gankable, either for being pushed back against your tower or having an easy grab/engage

If all your lanes will be pushed up you can think of a 5 camp into scuttle:

Red start:
➔ ➔ ➔ ➔ ➔ ➔ Gank

Blue start:
➔ ➔ ➔ ➔ ➔ ➔ Gank

I suggest you to always close with a gank if it's possible and then look for the second rift scuttler or a second jungle clear into recall. In case you started blue buff you will have ancient krug ready to clear before a potential recall

After the initial clear your goal is to impact the map the more you can. Do another full clear of your jungle to gain exp, try to catch all rift scuttler as it's very easy for you to clear them, and aim for lvl 6 asap.
If you have a good gank setup make use of it, it's ok leaving some camps up, and if you can spamgank a lane do it, but be careful to not waste time in bad ganks, as your goal is to early snowball and a bad gank will slow it a lot rather than not ganking and instead farming your jungle.
After 6 you should have global map presence like a Nocturne. Make enemies fear a Grand Starfall outta nowhere, and use it to cut their way back and force them to fight.

If you get a lead try to force ganks and fights, unless you are vs champs that you can't fight even with a lead (ex: Trundle, 2 items Graves, ecc.), every even fight 2vs2 or 3vs3 should be won(obviously consider first the teams composition).
If you have the chance for a 1vs1 duel only aim for short trades even if you are ahead, land your main combo and then back up if you can't finish your enemy with just another Comet Spear, as you will likely end the trade with your Aegis Assault on CD and if another enemy comes to help you'll not have defensive tools to escape.