Is ArcGIS available on Ubuntu?

At present ArcGIS Desktop is not supported on the Linux platform but you can install Server platform software on Linux such as ArcGIS Server.

Updated :-

For more details please check Similar question: ArcGIS for Desktop on Linux?

See also Desktop GIS for Linux (in Linux Journal)

Right now, only the backend software is available for Ubuntu (ArcServer, ArcSDK). This is because many enterprise-level companies run Ubuntu, SUSE, or other Linux servers and Windows workstations. However, ArcGIS is not the only fish in the sea. Using free and open-source software, you can do almost everything that ArcGIS can, and a number of things that it can't. If you already know how to use ArcMap, the learning curve going to QGIS or others is a lot less steep than you might expect.

I personally use an open source software stack on Ubuntu for a lot of my work. Once I have time to learn the Python syntax for QGIS (PyQGIS), I may leave ArcMap behind.