This is perhaps the most balanced 1v1 non-mirror matchup. The Terran poses a lot of threats to Protoss due to their versatility and unique abilities, including EMP Grenades that can cut shields down to size. If you want to be prepared against them, then here are some things to remember so you can beat the humans into red pulp.

Strategies

First of all, walling off may not be a good idea since Terrans have Siege Tanks. A more mobile defense is needed since they have the range to pick off your Photon Cannons from afar. Scout out your opponent so you’ll know what they’re planning to build, then you can go for what can counter those threats.

Getting an Observer out early is crucial to keep scouting since Terrans are good in transitions due to their flexibility. They also have units capable of cloaking, like the Ghost and Banshee. Both of these units are capable of doing massive damage in a short period of time if not detected and destroyed, so having that detector unit at hand is very important. Just be careful with Missile Turrets or your investment will be shot down prematurely.

Zealots and Sentries are a must in your army as they can address a lot of problems that Terrans pose in both the early and mid game. Research Charge for your Zealots and add some Stalkers with Blink into the mix and you got yourself an army that can dance around the Terrans. Zealots with Charge can surround and take down Siege Tanks, as well as hordes of Marines and Marauders. Blink Stalkers can also do that and also take care of Reapers, Hellions, and air units. Sentries can provide additional defense with Guardian Shield since all Terran military units have ranged attacks.

As things heat up in the mid-game, bring in Immortals and Colossi to bring in more firepower. While the smaller enemy units are toasted by the Colossus’ Thermal Lance, Zealots, Immortals, and Blink Stalkers can take care of the bigger threats. You can also use the Phoenix to neutralize air units and various ground threats with the Graviton Beam. Make sure you have a bunch of them so that one can bring it up with the Graviton Beam while the others turn it into swiss cheese.

In the late game, Terrans can mix it up some more with powerful units like Thors and Battlecruisers. You can also have yours with Carriers and the almighty Mothership. The former is very good at thinning out hordes of infantry and can pick away at larger units, while the latter have Mass Recall and Vortex to really bring in the pain when and where you need it most. But the most important unit by this time is the Void Ray, which is incredibly effective on enemy units with lots of HP. A battle between a bunch of them against Thors and Battlecruisers is a foregone conclusion — your Void Rays will burn them away with their Prismatic Beams.

So to review, you want a ground combination of Zealots, Sentries, Immortals, and Colossi to deal with most threats. Colossi can kill of Marines, Marauders, and Ghosts, while Immortals can take down mechanical units due to its powerful shields. Sentries help make your army last longer with Guardian Shield, as well as Force Fields if you have the micro for it. If you have High Templars, it is important to keep them busy as Psi Storm is always useful against most units.

Micro makes the difference in this matchup. The Terran is micro-intensive due to various useful unit abilities, but the Protoss aren’t pushovers here either. Most of your micro will be about focus firing to take out the biggest threats right away. Moving your Stalkers and Zealots in and out is important, as well as using your Sentries properly. For example, if you’re baiting enemies into a chokepoint you can have your Stalkers blink to that location while your Zealots give chase, then have your Sentries use Force Field at the choke point to cut the enemy army in half, then you can pick them off while the other half helplessly watch their comrades get cut down with extreme prejudice.

Your unit production must be reactive to what the Terran player is dishing out. You can go for a standard 2-gate 2-robo opener to get things started, which will churn out most of the units you need. You can build more Warp Gates later on, but two Robotics Facilities should do you well enough for most of the time. Just take note that you can’t make 10 Colossi, only to encounter Banshees and Vikings. You have to keep scouting out your opponent so you don’t get into that kind of situation.

Unit Counters

Marine

• Zealots with Charge upgrade can be used to surround Marines.
• Colossi takes out mass Marines with ease.
• High Templar can also take out mass Marines with Psionic Storm, especially in choke points.
• Sentries for support.

Marauder

• Zealots with Charge upgrade again, but less effective when Marauders have the Concussive Shells upgrade.
• Immortals can withstand attacks well due to their powerful shields.
• Colossi work well against mass Marauders.
• Sentries with Guardian Shield are great against their attacks.
• Air units are safe against Marauders, but are weak to Marines.

Reaper

• Stalkers are good against Reaper rushes. As time goes by the Reaper rush will be less effective and you should have enough Stalkers to pick them off.
• Photon Cannons will also help you defend your Probes.
• High Templars with Psionic Storm hurt Reapers a lot.

Ghost

• Observers at crucial locations to detect cloaked Ghosts. Remember that if you spot a Ghost just as it’s doing something, it may already be too late.
• Try to spread your army a little to minimize the effect of EMP.
• High Templars can kill Ghosts using Feedback, but can get kill by Sniper Rounds.

Hellion

• Stalkers can hunt down Hellions and help defend expansions and mineral lines. Blink makes things easier.
• Sentries with Force Fields can slow them down.
• Photon Cannons are like brick walls to Hellions.

Siege Tank

• Zealots with Charge can close in on Tanks in siege mode before they can get off a shot.
• Stalkers with Blink also can get close them quickly.
• Immortals are straight-up counters with their powerful shields.
• Air units can take them out. Phoenix with Graviton Beam renders them helpless, and Void Rays can take them out quickly.

Thor

• Immortals and Zealots to counter them.
• Void Rays do massive damage to Thors.
• Not much trouble with Thors in PvT, but beware of drops.

Viking

• Stalkers are your main defense against Vikings.
• Vikings can take down Colossi from a distance.

Banshee

• Observers ASAP!
• Stalkers to outnumber Banshees.
• Phoenixes for mass Banshees.
• High Templar can help with Psionic Storm.

Raven

• Stalkers focus-firing at Ravens is important. Use Blink to escape Seeker Missiles.
• Phoenixes to deal with mass Ravens and defend mineral lines.
• High Templars with Feedback.

Battlecruiser

• Void Rays are effective against them.
• Stalkers with Blink to take out lone Battlecruisers.

Supplementary Video

If you have the time, watch this hour-long video that explains Protoss macro play against Terrans.