With Debian- and Ubuntu-based distros, you can use Opera's repository to ensure that your system will always have the latest stable Opera version.
You can also always get the latest version from http://www.opera.com/download/ but in that case you won't be using the native system tools (apt, aptitude, Ubuntu Software Center) to do updates.
Installing via repository is the recommended way to install Opera according to the Ubuntu Community Help Wiki.
To install Opera, simply go to their download page here. Ubuntu will be auto-detected, and click on the big Download Opera button:
Choose the "Open With" option, and the file will automatically open in Software Center once downloaded:
Click on Install in Software Center, enter your password if asked, and then Opera will be installed:
In terminal:
Detailed up-to-date instructions are available here:
Quoting the Opera Knowledge Base:
You can also always get the latest version from http://www.opera.com/download/ but in that case you won't be using the native system tools (apt, aptitude, Ubuntu Software Center) to do updates.
Installing via repository is the recommended way to install Opera according to the Ubuntu Community Help Wiki.
Open the terminal.
Then: 64 bit.
Replace "amd64.deb" with "i386.deb" if you work on 32 bit.