[allwein]

You can disable WiFi quickly by swiping down (from the top right) to bring up control center and then tapping the WiFi button.

[B_Throwaway]

While Wi-Fi is disabled, auto-join for any nearby Wi-Fi networks is also disabled until:

- You turn on Wi-Fi in Control Center.

- You connect to a Wi-Fi network in Settings > Wi-Fi.

- You walk or drive to a new location.

- It's 5 AM local time.

- You restart your device.

https://support.apple.com/en-us/HT208086

[codnee]

Depends on what you call disable. Tapping in the control center will disconnect from WiFi but the phone will then connect automatically to any other network it knows.