Local money
The official currency is the Egyptian Pound (EGP).
Cash vs. card
Major hotels, upscale restaurants and large retailers seamlessly accept credit cards (Visa and Mastercard). However, Cairo still runs heavily on cash for everyday things — you will definitely want cash for local markets (like Khan El-Khalili), taxis, tips and small street vendors.
Tip: withdraw Egyptian pounds from a bank ATM once you arrive (airports and hotels have them), and keep a mix of small notes for tipping.