I think the best option if you don’t plan to stay a lot of time in really rural areas, AldiTalk will be your best Option (O2).
You can buy them at every Aldi store and if I remember correctly you can even activate them at the stores.
For example you can get 6 GB with voice and sms flat for 12 €.

This is awesome, definitely will take your tip for my trip to Berlin next week. Thanks!

By far the best deal was at the Saturn stores (we went to the one at Alexanderplatz). They had someone who activated the cards for free (and we only needed our passport), and also had a buy one get one free deal, so we got two Prepaid o2 cards for only €10.

Thanks Jules!

Great update – thanks!

That said, I lived in Germany for a year recently, and had a prepaid plan on Vodafone. They were okay, nothing exceptional. I tend to go with them when I go back because they’re cheaper than Telekom while having access to LTE.

For those asking about contracts for extended stays: Prepaid was the only option for me — contracts were 2 years minimum. The other thing to keep in mind if you go the contract route is that contracts work differently in Germany. You have to read the fine print very carefully and contact the provider (often in writing) many months in advance of contract end to notify them that you do not want to continue the contract. The assumption in Germany with pretty much all contracts is that the consumer *wants* to continue the contract, so they will automatically extend and you are on the hook for the full price of the contract if you haven’t notified them in the proper time that you don’t want to continue. They will sic collections on you if you don’t pay, even if you’re out of the country.

Also, whatever you do, do your research in advance. When we went to the local mall Vodafone kiosk to buy our cards a few years ago, the associate tried to steer us into a business contract that I hadn’t seen on their website, and he told us it would be no problem to cancel the contract if we could prove we’d moved out of the country. NOT TRUE!

Basically, the commissioned salespeople at any mobile provider will try to get you into whatever pays them the most, and will lie about the terms. By the time you’re snared into a contract you don’t want and can’t cancel until the end of 2 years or more, that associate will be long gone.

Buying your card at the grocery store gets around this, but the registration process can be tricky if you don’t have good wifi (as in, you’re on crappy hotel wifi). They need to be able to get a clear shot of your passport next to your face on a video chat. It took three tries for me when I bought an Aldi Talk card recently.

Last year I was in Ireland first and bought my Vodafone SIM there with absolutely no problem. If you have an opportunity to do that, do so — you can roam EU-wide with no extra charges.

Not that I’m aware of. You can buy esim service from a few international SIM companies that will cover Germany, but it’s more expensive than a physical local SIM.