How do I create a new folder using a keyboard shortcut?

Windows

Ctrl+Shift+N: Create a new folder in Windows Explorer.

Alternatively, use ALT+F+W+F on older Windows versions and MENU+W+F on the desktop.

Mac OS X

Create a New Folder shortcut using the System Preferences -> Keyboard & Mouse -> Keyboard Shortcuts panel. The system won't let you choose Cmd-N, but it will let you choose Cmd-Shift-N. Use that.

Desktop

The shortcut key should work there too.

On Windows 10
Windows 10 offers an alternative way that I just found. You can configure it yourself. It was standard setting on my system so most people might already have it working this way.
Then the shortcut is Alt+2 (note not F2)

This refers to the index of the items at the top bar of the windows explorer:

It can be configured by clicking the arrow next to it to show the item on top (screen shot from german system):

I have created an autohotkey script to remap Ctrl+Shift+n to Capslock+F12. You can remap it to any other key you want.

The key below is context-sensitive, meaning it will only work in Windows Explorer AND Windows Explorer file dialogs (open/save as).

#IfWinActive AHK_CLASS #32770
    Capslock & f12::
#IfWinActive AHK_CLASS CabinetWClass
    Capslock & f12::
    Send {Ctrl Down}{Shift Down}{n}{Shift Up}{Ctrl Up}
    return
#IfWinActive

To understand the syntax above, see below example,

;   Syntax - To have the same hotkey subroutine executed by more than one variant, the easiest way is to create a stack of identical hotkeys, each with a different #IfWin directive above it. For example:
    ;#IfWinActive ahk_class Notepad
    ;#z::
    ;#IfWinActive ahk_class WordPadClass
    ;#z::
    ;MsgBox You pressed Win+Z in either Notepad or WordPad.
    ;return

Hope you find this useful!

I believe this is a duplicate of Keyboard shortcut for creating a new folder or file? (Windows) and have flagged it as such, but seeing as this question is so old and has more views, I figured I could help more people by sharing my answer here:

The built-in Windows Explorer Control+Shift+N shortcut hasn't worked for me for years. If you Google this, you can find lots of people in similar boats. Perhaps there's some app I'm using that is eating the keystrokes, but I've never been able to find it.

Once I found this trick, I decided to create an autohotkey (v1) script to make Control+Shift+N work correctly again:

#IfWinActive ahk_exe Explorer.exe
+^N::
SendInput {Blind}{Ctrl up}{Shift up}{Alt up}{n up}
SendInput {Blind}{Alt}2

Here's the line by line explanation:

1. If Explorer.exe is the active window
2. And you press Control+Shift+N
3. "Key up" Control+Shift+ALT+N so they don't interfere with the next line.
4. Press ALT, 2

You can put this script in a ".ahk" file and double click it to start it. Follow these instructions to have it run automatically when Windows starts.