Most tutorials or documentation will suggest using "admin" as the username and a blank password to log in to Mikrotik for the first time. In some cases, it will succeed, but recently, you might receive a "username or password wrong" error with an empty password on a brand-new MikroTik router; it is likely because newer models no longer use a blank default password.

Solution: Locating the Unique Factory Password

Many newer MikroTik devices now come with a randomly generated, unique password pre-set at the factory for security. Look for this password in the following locations:

A sticker on the device: Usually located on the bottom or side near the serial number.
The product packaging: Check the label on the outside of the retail box.
The "Quick Guide": Found on the paper documentation inside the box; read to get suggestions on where the password has been written or what they are, in case they are stated in the guide.

Below is a sample from a new router I purchased. The password is located on a sticker at the bottom of the device.

Important:

If the password contains characters like 0 (zero) and O (capital o), or 1 (one) and l (lowercase L), try both variations, as they can be easily confused on printed labels.
The username is also suggested there, so if there are any changes from the default value of "admin" from the factory, you get all the credentials in one place.