Foreigners in Korea

Depending on how long you're staying in Korea and what you need to do while in Korea, you may need a SIM card. Renting a WiFi egg is great if you are only visiting, but if you are applying for a job, for instance, you may need your own Korean phone number, in which case you will need a SIM card.

Prepaid SIM cards

Available to visitors

Some (few) SIM cards are available to foreigners who are only visiting and do not have an Alien Registration Card.

EG

An EG SIM card is a great option for foreigners who are staying for a short period of time, as you do not need any help from a Korean to get it. It is available at many (not all) GS25 convenience store locations and at Incheon Airport. It can be activated by sending a picture of your passport to a secure website online.

The EG SIM card seems to work with all phones without any problem.

Unfortunately it is relatively expensive. If I recall correctly, my EG SIM card in 2016 was 35,000₩ for which included 1GB of data and no voice (any use of voice reduced the available data).

Not available to visitors

Many prepaid SIM cards require you to either be a Korean citizen or a registered as a foreigner. A Korean citizen can apply for the card on behalf of a visitor, however.

Mmobile

Mmobile is an MVNO using the kt (aka olleh) network. As it is a discount brand, the SIM cards are not available in stores, but will arrive in the mail after filling out a form online. It takes about 3 days to process and arrive in the mail.

The Mmobile SIM card did not work with my unlocked Canadian Moto G (2015) for unknown reasons. Discussions with kt technical support suggested they may need to add the IMEI specially, but the problem wasn't resolved, so I bought a new phone instead.

The price is approximately 25,000₩ for 1GB of data and 20 minutes of voice.

Second-hand phones

Buying a cheap second-hand phone is a great idea, particularly if you need a phone only while you are in Korea. The price of a second-hand modern (less than 4 years old) can be as little as 50,000₩ at an electronics market.

Seoul electronics markets

There are 2 major electronics markets in Seoul where you can find cheap second-hand electronics:

1. 용산전자상가 (Yongsan Electronics Market), close to 용산역
2. 강변 테크노마트 (Gangbyeon Technomart), immediately beside 강변역