Where is SVN on OS X Mountain Lion?

Install the latest Xcode from the Mac App Store.

Go to Xcode » Preferences » Downloads » Command Line Tools » Install.

If you don't want to download/install Xcode, you can always just download Command Line Tools for Mountain Lion from Developer Downloads.

If you have Xcode installed and if you use bash :

$> vi ~/.profile

add this at the end of your .profile PATH="${PATH}:/Applications/Xcode.app/Contents/Developer/usr/bin/"

$> source ~/.profile

It should be working

Also checkout Homebrew for these type of packages :

brew install svn