ORIANNA MAINS PLEASE I HAVE NEARLY A 0% WIN RATE VS. ORIANNA.
I TRY TO PLAY HER AND HER BALL HAS THE RADIUS OF A FUCKING PIN
BUT SOMEHOW I GET HIT BY EVERY BALL AND GET 100-0 IN 2.5 SECONDS VS. HER EVERY GAME
FUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUCKING TIPS PLS
If you have not played her I would recommend that you go and do so for a few games to get a feel for her Q range and its move speed, then depending on champion try to keep the required distance to avoid a QE combo so you don't get harassed out. every time she cast Q you should be moving to position to dodge her next cast, means not getting to close to her or the ball. Otherwise your options are bully, burst, mobility. She is a strong champ and I wish you the best of luck.
I do just fine vs oris as 
as well as the champs other people have metnioned. learn how to count her timer, and get good.
A champion that can both trade and shield himself, where ori has to decide whether to shield herself or throw out her ball. Seriously, his trades vs. Orianna are so good. Sadly, he isn't in the best spot at the moment.
That ball is quite literally everything It's her way to poke, space, literally her kit is based around that orb. The best way to deal with it is to stay the fuck away from it. Ori can only control a certain area around the ball. Understand where it is, and where she is. Without the ball she is powerless.
Early laning will basically determine whether or not she bullies the fuck out of you. Using the ball takes mana. She cannot control the ball when it's in motion. She is defenseless WHILE the ball is in motion. Give your opponent options: either focus the minions, or focus yourself. Do not let her control the early stage. Get her to waste her mana.
If Ori is a smart person, this turns into a skill matchup. There will be times Orianna's simply will punish with little room for retaliation. If you cannot pressure her before 6, after 6 your option is to keep even with farm and let her be aggressive in the lane. Stay even, and focus her in the team fight. Her ult can and will mess you up if you don't have eyes on the ball.
TL;DR, the ball is the champion. Do your best to stay away from it.
dont stand still. play champs with gap closers. 
. honeslty or just carry exh 
and exh her ult . but zed IS A REALLY GOOD PICK INTO ORI imo you can dodge pretty much everything she has if played right
Lots of bad advice in here lol. Squishy melees are generally a no-go, regardless of whether they have gapclosers/mobility or not, and happen to be some of the easiest matchups for a fairly burly control-mage like her. If you insist on playing an assassin, be wary if she's taken Barrier/Heal as she's deceptively durable when she returns her ball and gets the shield+resists in tandem with it.
The best way to deal with Ori is an artillery mage--they can zone her out of farm very early on without taking any return damage--as long as you position properly--and they can shove lane much easier to deny her CS even further. 
are extremely good examples--they even pack some emergency CC for when she tries to close the gap; there's not much she can do if a champ is far away and they have even the lightest CC to peel themselves with before she can make a move.
EDIT: Also uuh....she tends to get more and more oppressive as a game drags on, so either starving her of gold and/or having a teamcomp that can win it earlier than later is your best bet.
Play ziggs or xerath. They out range her and wave clear better than her. If she tries to shove back, she will run out of mana before you. This is the safer method since ori is mid range and her ball moves super slow, so it's easy to dodge if you have the range advantage.
If you have good mechanics you can also play assassin like zed lb ahri talon.
Faker played ori at MSI this year. He was solo killed a couple times when the enemy mid laner was lucian. The second time lucian killed Faker's ori while tanking tower shots lel.
Wait until her battery dies
You don't necessarily have to beat her in lane. If you can out shove her and roam, you don't even need to beat her in lane, you just out roam her and snowball your team.
Laning versus Orianna requires you to keep careful track of both her and her ball. Smart Orianna players will park the ball a bit outside of it's cast range on your side of the creep wave, and then wait for you to step up and try to cs (or trade with her). When you do, they will step up so that your destination is in their Q's cast range and then cast it and back away. If you try to run at her, the ball will hit you and she will likely add her W to the mix for more damage unless she is currently low on mana or otherwise feels inclined to not cast it. You can bait this out by feigning moving up early and then dodging her Q when she goes for the harass, it's cooldown and mana cost are both pretty low though, so your window to exploit the fact that she just moved the ball is short (6 to 3 seconds base, depending on her Q rank).
The thing to keep in mind when trying to avoid being hit by her ball is that, like any other projectile skill, it her Q, Command: Attack, has a travel speed, and hence the further the ball is from you, the longer it will take to reach you, giving you more time to react and move out of its path. You can exploit the usual 'ball-parking' strategy a bit by first approaching from one side of the lane to bait out her Q, then once baited, move to the far side of the lane, maximizing its travel time should she try to cast it on you again. Moreover, if/when she does, simply switch sides of the lane again.
The other thing to be keenly aware of is her passive. It makes trading basic attacks with her counterproductive for most AP mid laners as she will win basic attack trades against them handedly. For this reason, it is preferable to stick to short trades against Orianna (or all-ins if you have the burst/DPS).
Probably too late to the party, but your local ori main is here w her own anecdotes:
I have never NOT fed against Talon, Zed and Ekko. I can't ever seem to 100-0 them quickly enough and I'm just way too squishy. Pick someone with burst and even a fraction more sustain than her.
Her ult is on an insanely low cooldown, especially once she gets her cdr up. if you're playing someone squishy, it's going to kill you. If you're not, it's going to secure a kill for her teammates. Always assume her ult is up and stay the FUCK away from her until you see her use it. Even if it means people spam pinging enemy missing, it's never worth feeding the Orianna.
I would say most importantly, don't get hit by her E. Getting hit by her E is entirely your fault, to be honest. The thing's slow as hell and moves in a straight line!
If you're playing someone who counters her, she's likely going to play passive and farm for hours. DON'T LET HER. She's a painfully average champ until she gets her 
, so bully the hell out of her and stall her as long as possible. It should seem like obvious advice, but only getting a morello 18 minutes in is devastating.
TLDR don't 1v1 her when she gets morello, bully the living hell out of her until she does, then beg for ganks lol (or take her up for yourself, once you get a feel for the ball she's super engaging and fun as hell)
Okay I admit I'm really fucking tilted right now, but Orianna is the only champion that consistently makes me go X/9/X in lane. NEARLY EVERY TIME. How is she not OP? She outclasses Viktor in nearly every category. Faster combo, better speed boost, larger shield, more damage, harder CC, better early game, better late game, better trades, etc. I can't find a single way to beat her.
Once the ball leaves the doll version of her she has lower MR and armour.
Orianna is only as skilled as the person playing her.
has some serious ways of punishing her for the ball being moved around.
Thanks for the general tips everyone. I have already tried playing as her for several games over the years. I guess I need to study her numbers again.
summoner school is a good sub reddit to get tips. don't post in all caps and rage, but yeah.
just google summoner school and ask there for tips on how to beat orianna. they have players ranging from bronze to challenger who can give you all kinds of perspectives.
The boards will be like: 
HER ULT TIMER IS JUST TOO LOW!?!?!?!?
Dude has like a 1.3 AP ratio on his ultimate, which by the way- also applies his passive for additional damage which by the way- applies true damage to researched specimen. Oh by the way- his ult can reach 44 seconds, just like Ori.
