ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)

Note: For MySQL 5.7+ please see answer from @Lahiru to this question. That contains more current information.

For MySQL < 5.7:

The default root password is blank (i.e. empty string) not root. So you can just login as:

mysql -u root

You should obviously change your root password after installation

mysqladmin -u root password [newpassword]

In most cases you should also set up individual user accounts before working extensively with the DB as well.

I was able to solve this problem by executing this statement

sudo dpkg-reconfigure mysql-server-5.5

Which will change the root password.

You have to reset the password! steps for mac osx(tested and working) and ubuntu

Stop MySQL using

sudo service mysql stop

or

$ sudo /usr/local/mysql/support-files/mysql.server stop

Start it in safe mode:

$ sudo mysqld_safe --skip-grant-tables --skip-networking

(above line is the whole command)

This will be an ongoing command until the process is finished so open another shell/terminal window, log in without a password:

$ mysql -u rootmysql> UPDATE mysql.user SET Password=PASSWORD('password') WHERE User='root';

As per @IberoMedia's comment, for newer versions of MySQL, the field is called authentication_string:

mysql> UPDATE mysql.user SET authentication_string =PASSWORD('password') WHERE User='root';

Start MySQL using:

sudo service mysql start

or

sudo /usr/local/mysql/support-files/mysql.server start

your new password is 'password'.

NOTE: for version of mysql > 5.7 try this:

update mysql.user set authentication_string='password' where user='root';