The first time I boot up my Raspberry Pi I get a login screen.
What username and password should I use? That is, what is the default password for Raspberry Pi?
This depends on the distribution you have downloaded. The default passwords for common distributions are as follows:
Distribution | Username | Password
Debian Squeeze | pi | raspberry
Arch | root | root
QtonPi | root | rootme
Raspbian | pi | raspberry
OpenElec | root | openelec
Straight after logging in you should change your password by using the passwd command at the shell prompt
With Raspbian, the username is
pi, and the password is
raspberry. You can change the password by running the command
passwd, using the
raspi-config tool, or the graphical
Raspberry Pi Configuration tool. On Arch, the username is
root and the password is
root. You can also change the password with the command
To add to the answers about 'Beware if you are using a German keyboard: In this case you have to use pi / raspberrz', they are omitting to say that this is an issue after first boot because the user cannot yet have told the pi that a German keyboard is attached. The pi defaults to expecting a UK English keyboard. Once that's changed, all the letters and symbols will be correct.
The same issue also applies for other language keyboards - eg symbols in the wrong places - until the correct language driver is installed (eg, using sudo raspi-config). But it matters most for the password because the default contains a 'y' and needs the 7th key along on 2nd row (which is marked Y on the default English and many other keyboards but Z on a German keyboard).
Users with French 'AZERTY' keyboards will have to substitute for the 'A' in raspberry (press the 2nd key on 3rd row, whatever it is marked ...)
With Raspberry pi OS (previously called Raspbian) release of April 2022, the default user and password was removed, making it impossible to login via uart directly after installation for instance. It is necessary to login via the graphical UI and to create a user account there first. See https://www.raspberrypi.com/news/raspberry-pi-bullseye-update-april-2022/