Before you start

Passport plus a valid Saudi visa (visitors), or your physical Iqama / National ID (residents)
The handset on which you can complete biometric/identity verification
An unlocked, GSM-compatible handset (eSIM-capable if you want an eSIM)
For postpaid: an active Iqama, and usually a Saudi bank account or card for the recurring direct debit

Step-by-step

1
Pick prepaid or postpaid (and the right carrier)
Three networks cover Riyadh — STC (prepaid brand 'sawa'), Mobily, and Zain — plus MVNOs like Lebara, Virgin and Salam. Arriving newcomers almost always start prepaid: it needs only your ID and activates on the spot. A postpaid contract gives bigger data and bundled handsets but requires an active Iqama, so it is a second step once residency is formalized, not a day-one option.
In personWho: YouDecision onlyPrepaid starter packs roughly SAR 30-50; visitor tourist bundles roughly SAR 35-190
2
Buy and register the SIM in person with biometric verification
Go to an official carrier store or a staffed airport kiosk at Riyadh (RUH) — not a random stall. Present your passport+visa or Iqama; the agent scans your ID and captures your fingerprint/biometric, which is checked against the national identity system before the line is allowed onto the network. This biometric real-name step is mandatory for residents and visitors alike. The number is then linked to you and activated, usually within minutes.
In personWho: You, with a carrier sales agent15-30 minutes in storeIncluded in the SIM/pack price
3
Activate, recharge, and (optionally) self-serve via app
Top up prepaid credit via the carrier app (mySTC, Mobily, Zain), online, ATMs, or recharge vouchers in supermarkets. Residents can self-register or move a SIM online through the carrier app using Nafath/Absher instead of returning to a store. eSIMs are issued by all three majors at staffed points of sale; residents can often activate an eSIM in-app, but visitor app activation is frequently blocked by a Saudi-ID check — so as a visitor, get the eSIM provisioned in person.
Mobile appWho: YouImmediateRecharge amount only
4
Upgrade to postpaid once your Iqama is active (and verify your lines)
With an active Iqama you can sign a postpaid contract in-store or via the carrier app, typically with a Saudi bank account/card for the monthly direct debit. Whichever route you take, confirm what is registered to you using CST's Mutasil portal ('Inquire about my numbers') — it lists every number tied to your ID at no cost, so you can catch lines opened in your name without consent and stay under the per-ID cap.
OnlineWho: YouSame day in store; Mutasil check is instantPostpaid plans commonly SAR 100-300+/month depending on bundle

Documents you’ll need

Passport + valid Saudi visa (visitors) or physical Iqama / National ID (residents)
Fingerprint / biometric captured live at the point of sale
Border (entry) number — useful for visitor SIM registration on arrival
Saudi bank account or card for postpaid direct debit (postpaid only)

Things most newcomers don’t know

Saudi makes you give a live fingerprint to own a SIM — it is a biometric, government-linked real-name system, not a casual purchase.

Every line is verified against the national identity system before it can join the network, so you genuinely cannot get a working number without showing up in person and being biometrically matched. Budget for a store visit; you can't fully do this remotely on arrival.

Source: CST (Communications, Space & Technology Commission)

Register every SIM in your own name — borrowing a line or using one in someone else's name quietly breaks the rest of your setup.

Nafath/Absher logins, OTPs and bank verification expect the number to belong to the same identity. A mismatch means failed authentications for government and banking services exactly when you need them, with no obvious error pointing at the SIM.

Source: ksaexpats.com

You're capped at only a couple of lines per ID, and they all count — check Mutasil before assuming you can add another.

Residents are generally limited to about two lines per Iqama (prepaid and postpaid both count), and visitors to roughly two per passport. If you're at the cap, a new purchase is refused until you release an old line — and Mutasil can reveal lines opened in your name without consent.

Source: CST Mutasil

If your fingerprints can't be captured, CST offers a SIM Authentication Code via Nafath as the official workaround.

Worn or unreadable fingerprints are a real blocker at the counter. Rather than being stuck, you can obtain a temporary authentication code through Saudi's National Digital Identity to issue the SIM — a non-obvious fallback most store staff won't volunteer.

Source: CST SIM Authentication Code Service

Common mistakes to avoid

Assuming you can activate a SIM or eSIM fully online as a newcomer — biometric capture means visitors and first-time registrants must do it in person; visitor app activation is often blocked by a Saudi-ID check.
Using a SIM registered to your employer, a friend, or an agent — it can break Nafath/Absher and banking OTPs, and you don't truly control the line.
Trying to sign a postpaid contract before your Iqama is active — postpaid needs the Iqama (and usually a Saudi bank account), so you'll be turned away and should start prepaid.
Letting an old prepaid line lapse, or ignoring lines on Mutasil you didn't open — you can hit the per-ID SIM cap and be unable to register a new number until you clean them up.