Before you start

A valid passport or national ID for the mandatory identity verification
A German address you can enter at sign-up (a hotel or Airbnb is fine for prepaid)
For a contract (Vertrag): a German bank account, a SCHUFA record and usually your Anmeldung
An unlocked phone (or one that supports eSIM)

Step-by-step

1
Start with prepaid — Aldi Talk or congstar
Buy a prepaid SIM or eSIM at a supermarket, kiosk or online. Aldi Talk and congstar (a Telekom subsidiary) both run on the strong Telekom D-network and are the go-to before you have a bank account or SCHUFA. No Anmeldung, no credit check, no commitment.
In personWho: YouSame dayStarter pack ~€10–20; plans from ~€8/mo
2
Verify your identity (PostIdent or VideoIdent)
Before the SIM activates you must prove your identity, as German law requires for every card since 2017. VideoIdent is a 5–10 minute video call where you show your passport, but not every nationality is accepted; PostIdent (free, ~10 min at a Deutsche Post branch) works for everyone. In-store registration is instant if you buy at a carrier shop.
OnlineWho: YouMinutes to ~48 hours to clearFree
3
Activate the SIM and top up
Insert the SIM (or install the eSIM profile), wait for activation once verification clears, then load credit or buy a flat-rate bundle in the provider's app. Your German number is live and you can hand it to your bank, employer and the Bürgeramt.
Mobile appWho: YouActive once ID check clearsPay-as-you-go or bundle ~€8–20/mo
4
Later: switch to a contract once settled (optional)
After your Anmeldung, a German bank account and some SCHUFA history, a postpaid contract with Telekom, Vodafone or O2 (or budget arms like congstar) can give more data for less. Contracts run a SCHUFA check and typically lock you in for 24 months, so there is no rush.
OnlineWho: YouAnytime after settling in~€10–40/mo depending on data

Documents you’ll need

Valid passport or national ID card (for identity verification)
A German address for the sign-up form
German bank account / IBAN (contracts only)
Anmeldung / Meldebescheinigung (usually asked for contracts)

Things most newcomers don’t know

Every SIM must be registered to your verified ID — even an Aldi Talk one from the till.

Since a 2017 change to the Telekommunikationsgesetz, no German SIM activates until the buyer's identity is verified against an official ID document via PostIdent, VideoIdent or a shop. The supermarket SIM is cheap, but it is not anonymous — budget 10 minutes for the ID step.

Source: Bundesnetzagentur (Identverfahren Prepaid) / TKG

Prepaid is the newcomer move because a contract needs a bank account, SCHUFA and Anmeldung.

A postpaid Vertrag runs a SCHUFA credit check and wants a German bank account and usually your registration — none of which you have on arrival. Prepaid (Aldi Talk, congstar) sidesteps all three so you get a working number on day one and a contract later.

Source: provider terms / Bundesnetzagentur

VideoIdent can reject your passport — PostIdent accepts everyone.

Automated VideoIdent only supports certain nationalities' documents, and travellers are sometimes bounced mid-call. PostIdent at a Deutsche Post branch is the universal fallback: free, in-person and accepts any valid passport, at the cost of a short queue.

Source: carrier verification guides

An eSIM gets you online the moment you land.

All three networks (Telekom, Vodafone, O2) sell prepaid eSIMs you can buy and install before arrival, so your phone connects at the airport without hunting for a shop. The same ID-verification rule still applies before full activation.

Source: carrier eSIM pages

Common mistakes to avoid

Assuming the supermarket SIM works straight away — it stays dead until you complete the ID check
Trying VideoIdent with a nationality it does not support, then being stuck; use PostIdent instead
Applying for a 24-month contract before you have a bank account, SCHUFA history and Anmeldung
Letting a prepaid SIM lapse through inactivity and losing the number