I've been struggling with mass Stalker players for some time now. 
 
While it won't be a problem to fungal the growth out of them with Infestors, I'm a Terran player myself and can't come up with a solution. Perhaps a mass Marauder will do, but you see, I can't be sure that he won't send a Void as well. I've tried various defenses, but they all turn useless when they blink inside my base. There are always cheap Observers patrolling so even Banshees don't work.
 
go gg gl gg gogogogo

A mixed bowl of marauders and marines with stimpacks will both cover the stalkers and a few extra VRs. Of course, adding a few dropships helps as well.

Ghosts w/Nuke. People who mass stalkers are usually imbeciles who don't know how to do anything else or how to micro.
 
Or at least as far as my experience goes.

3 Xanax and a lortab

Marauders, medivacs (from a reactored starport.  if he sends void rays just switch to viking production and kite the voids), and if it gets late enough into the game ghosts to emp shields.  Marauders demolish stalkers thanks to their bonus against armoured units. It's almost as ugly as marauders versus roaches, where marauders just don't die and kill double their numbers in roaches.
 
Believe it or not, tanks actually work well in defensive situations.  They chew through stalkers, which is one of the reasons why the 1/1/1 is so hard to stop, because the tanks kill your anti-air so fast and then the banshees kill all the ground units. 
 
For zerg just do roach/infestor (if he has zealots with stalkers) or ling/infestor (if he only has stalkers, the lings will hold them up long enough to get fungals off) and lock the stalkers down and kill them.  You can infestor your way out of any situation if your micro is good enough. Don't forget after you kill all his stalkers (and his macro will likely suck if he only made stalkers) to go infested terran bomb his expos to salt the wounds.  It's quite satisfying when they swear at you as they lose their expansions in record time.

Stim marines rip through void rays and marauders hard counter stalkers. Just polish your basic MMM build to perfection and you shouldn't have trouble.

Tanks. 
 
As the marine in Halo 3 says - "TANK BEATS EVERYTHING!"

@antikorper said:

I've been struggling with mass Stalker players for some time now. While it won't be a problem to fungal the growth out of them with Infestors, I'm a Terran player myself and can't come up with a solution. Perhaps a mass Marauder will do, but you see, I can't be sure that he won't send a Void as well. I've tried various defenses, but they all turn useless when they blink inside my base. There are always cheap Observers patrolling so even Banshees don't work. go gg gl gg gogogogo

Some replay files would be useful, though judging from that line, it sounds like you're just not having an active presence on the map and letting the blink stalkers run wild while you stay in your base. Keep a unit or two in front of his base to see when he moves out, and keep a marine on each watch tower.

Stim Marauders will cut those fools up, especially if they have medivacs to help em out.

Seems this comes up fairly often. Though a replay would help, you really can't go wrong with stim marauders and medivacs. Tanks for support, too.

If your opponent just makes a lot of one unit, it's really easy to stop unless you don't scout it.

Blink stalkers?

If it is an all in then just throw down some bunkers with marauders at the ramp and try to keep an observer from checking the high ground and allowing blink up... defend as best you can against that on certain maps. Use your scans/turrets to stop that observer. Marauders OWN.

If its a longer game and he is on 2 bases or even 3, then work on your macro because you should be able to get enough Marauders/Marines/Medivacs to stop mass stalkers dead cold.... they need to get colossus or something to deal with that bio ball.

Also, if they go Void and blink stalker then they just used a lot of money, and that means you should be able to stop that with MMM.

Btw, the new patch is gonna make blink take longer which will mess up timings for a little while.

@DG991: Any word on when the new patch may be coming off the PTR?

Make an infestor

everything owns blink stalker if you're positioned correctly.  the problem is their hyper mobility, just try to keep control of the towers and/or have patrolling scv/marine.
 
1.  they rarely have more than one observer in your base, scan and kill it.
 
2.  position your units ready to intercept the blink into your base
 
3.  get lots of free kills
 
4.  expand

you can try landing your command center on them to squish them

Contact the police ASAP and tell them about the issue. Most likely they will send a police unit to watch your house as the stalker acts. I also suggest getting a security system such as cameras to protect yourself from stalkers.

Contact the police ASAP and tell them about the issue. Most likely they will send a police unit to watch your house as the stalker acts. I also suggest getting a security system such as cameras to protect yourself from stalkers.

Just occurred to me, you could do the A-build, where you only get marines; research combat shield and stimpacks and upgrades. A shitton of marines kills stuff fast, and IIRC their DPS should outweigh stalkers by miles.

Gosh guys, I'm not exactly great at it or anything but I somehow have managed 650 wins and I've only used Zerg this whole time. I just don't have much luck with the infestor against stalkers. For me, mass stalkers will always be able to shoot my army which would include roaches in some cases. Stalkers soak up banes and hydras are almost useless. If anyone could correct me I'd appreciate it.

See, I usually get mass ling with my infestors because lings are sooooo effective against them. But if the other guy has tanks for support in a team game or thors, I'm pretty much toast.

As an aside, I hear Jennifer Anniston has mass stalkers and her overlords usually take care of them....just a thought......

I call in E-Honda to give the 1000 fists to the man berries. 
 
There are no survivors.

Just make marawdrs d00d

I call in E-Honda to give the 1000 fists to the man berries.  There are no survivors.

MMM will rape mass stalker

Marines and marauders, really.

Hmm yeah, the marines marauders worked quite well. The problem was that I went 5racks and there were voids harassing all over the place.
 
Anyhow, thanks for confirming that the marauders are the best counter ;)

Hmm yeah, the marines marauders worked quite well. The problem was that I went 5racks and there were voids harassing all over the place.  Anyhow, thanks for confirming that the marauders are the best counter ;)

hmmm If you let your oppenent "mass" anything your not playing aggressive enough. MMM drop/harrass, force him into either losing the game or switching tech to collosus/void, a starport w/reactor will finish the game off.  
 
at ~12min in the game how many rax you have running?