Hi guys. This is my first build and I'm just saying that I'm going to keep this as simple as I can. I find that very often all I need from a build is some Items - Masteries - Summoner Spells Suggestions and maybe a simple explanation why you want to pick those, works like a cheatsheet for me.
So thats what I will attempt to do here.

I've seen a couple builds for leona out there. I don't fully agree with any of them. I found some with same items I use but they had different masteries. So I thought I'd make my own for fun.

Please be lenient with me as its my first guide and read the whole thing before you decide if it's helpful or not. I will chosee the "Require comment to vote" option for the first 20 votes so I can get feedback for my build and not just plain votes. I hope you like my choices.

In my opinion this is the best summoner spell in the game as it can be used both offensively and defensively and its very sudden so you have the element of surprise.

For 5v5 Its extremely important that at least one of your teammates has this. It should be the tank in general or the dps if you are intending to backdoor a lot...You're the tank so grab this one and save a turret from getting backdoored or teleport to a teamfight where you are usually much needed.

For 3v3Since the map here is pretty small you don't really need teleport. I find fortify to be an extremely useful spell for tanks and especially stunners. It has a great passive for farming (more dmg to minions). It can be used to save a turret and buy valuable time when the whole team is dead and the opponents are pushing. With the extra point in def mastery you get that super splash damage that can kill a low life opponent even if hes not tanking the turret.
And last but not least, lets say they turret dive to kill you. Immediate shield and stun after they hit u once (either with you ulti if they are many or just your Q or both of them!) and then use Fortify to splash the hell out of them...

If you still don't like them you can use whatever you want i guess lol. Its important to use summoner spells correctly so anything works as long as you are good at using it and timing it i guess. (Yes! Even heal!! :D)

I like the defensive standard ones that you can see above and I also like the extra exp and gold from the utility. Plus if u get Fortify u can fit that in too this way. Your early damage is just fine as it is you don't really need offensive imo.

Runes hmmmmm.... These are the only ones I've tried to be honest and they work pretty well. I go with Flat Health quints for extra tankiness. I kinda need some CDR in this build so there you go glyphs. Penetration cause early u got quite an explosive magic damage combo and last but not least mana rege seals so you wont have mana problems a lot.

So basically I put one point tofirst for the early game ganks. 1 stun is very useful especially if your teammates know how to focus well :P

The I openso you can land some early game stun combos.

Then you basically max outbecause its you're main tanking and farming skill and the duration if you learn how to use it right is awesome.

After that you could go forfirst to reduce its cooldown but I prefer going forbecause it makes more damage and I like the burst that your combo makes for harassment.

Of course you level up your Ulti whenever you can.

I start off withand a potion.

Then I rushto take full advantage of the extra gold plus I really like this item on a tank with low cd skills like leona. You get health regen and mana regen so you can stay longer in lane and be aggressive with your skills...

Boots time!!
I getSince leona is melee and you will often be right in the middle of a fight using yourtenacity will be very useful if they focus their cc on you (which is actually a good thing ofc) and magic resist too cause we all know that casters can be really annoying early game when you are melee.

Then comes the item that many find useless but I personally love.
not only gives you a little bit of everything which is very useful early-mid game but also gives that bit of everything to your teammates, making them hit a bit harder and be a bit tankier.

Right now you got a bit more magic resist than armor.
fixes this "problem" and also gives a huge amount of life to make you survive the damage that comes through your armor and resistance (which with your early maxedis pretty decent)
But sunfire also makes you a much better farmer and spikes up your damage output if you consider that you have 2.5 stuns so your opponent will stay with you for quite some time...

And thats it. You're done with your core build. Right now you are balanced in all aspects and you just need to see who you're playing against and who is doing better and has more kills from the opposing team.

VS CASTERS
go forturning it into aor a.
I usually go for FON cause it gives you that extra movement speed which helps cause you're a melee stunner...

VS DPS
go forturning it into either aor aor a
Here it depends on what kind of dps your facing. I usually prefer Randuins for the extra life the CDR and the cool Active that fits very well with your standard skill combo (will explain that later). But if for example you got a squishy ranged one then Thornmail can be pretty good. If you have an attack speed based dps (not pure dmg) then frozen heart's debuff can be very good.

If you think you are doing well at a certain moment and you don't really need much more armor or magic resist a nice option would bewhich still gets you tankier but also gives you a bit more damage and a cool passive that also you to keep your enemies close to you sunfire for longer after you catch them with your combo.

And as your last item I would recommend turtninginto aYou also get a nice active here when you're chasing and you badly want to stun someone or when your team are running for their lives...lol

Or if you really want more damage go forsince you will already have a pretty big amount of health.

You main harassment combo will be++
But you have to make sure you do it fast because smart opponents will figure it out when you open your shield and move away from you before you can reach them with your zenith blade.
If you find out that you can't line that up then just use+and after you get to the opponent useto stun him. This will save you some valuable reaction time.
If you still find that your opponent dodges it fast enough just go for++
This way you get to him more suddenly so maybe you can catch him offguard.

This combo is your whole game and if you're going for the kill or if you are using your combo to tank a teamfight then you might want to use yourright after your get there.
If you're going for a single kill then use your ulti immediately after you Q wears off.
If you're in a teamfight just make sure you gather as many opponents as you can around you before you use it. Sometimes it is really clutch to use it when you're already used your combo and tanked a lot of dmg and you have low health. Most of the times they won't care you are the tank then so they will come for you. This way you can get the whole team with your ulti and then flash away and leave your teammates clean up for you.

Last but not least if you have Randuin's Omen then don't forget to use the active after you combo in a teamfight. If you used your ulti right then you should have a lot of opponents near you so slowing all of them is a big plus for your teammates trying to kill them...

That's basically it.
You have a lot of burst early and a great 4 skill combo so don't be afraid to be aggressive with Leona!

Please rate positively and give me your "welcome new builder" cheer! :D