Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
This is a tank build for Olaf that i've been using for a while and I love it. I love the fact that you have a large amount of health which really helps in teamfights. You might think that having alot of hp will get you eaten up by Madred's but with the Thornmail and your own skills you shouldn't have a hard time suriving.
I love to start out with some HP reg and it makes you able to use reckless swing more often without getting damaged too much when spamming it. When you're able to use reckless swing more often you are also able to get creepkills easier which will get you your Phage fast. After this you build your Phage into a frozen mallet for surviveability and a 100% chance on slowing them with each hit. This will help you support your team by having hp and slowing the enemies. Since you don't have alot of armor yet your next item will be a Thornmail. It will help you against those annoying autoattackers and it works so good with a Warmog's. BUT, if you are up against lots of high damaging casters you should get a Force of Nature instead. After that you get your second Warmog's for the incredible health it will give you (over 5000) and it works so well with Vicious Strikes. If you even got so far as the second Warmog's and the game continues after that you should get Atma's Impaler because it will give you lots of damage and that extra crit chance to make you drop some of those squishy mages and dpsers really fast + the extra 45 armor that can be very usefull.
This is NOT a completed build but I will publish it for advice and suggestions about how to improve it further and because I want to know how it works out for you.