Change the navigation bar's font

The question is plain easy and simple, the answer unfortunately not.

How can you change the font of the text in the UINavigationBar?

From iOS 7 and later:

NSShadow* shadow = [NSShadow new];
shadow.shadowOffset = CGSizeMake(0.0f, 1.0f);
shadow.shadowColor = [UIColor redColor];
[[UINavigationBar appearance] setTitleTextAttributes: @{
     NSForegroundColorAttributeName: [UIColor greenColor],
                NSFontAttributeName: [UIFont fontWithName:@"Helvetica" size:20.0f],
              NSShadowAttributeName: shadow
                                                      }];

From iOS 5 and later:

 [[UINavigationBar appearance] setTitleTextAttributes: @{
                                UITextAttributeTextColor: [UIColor greenColor],
                          UITextAttributeTextShadowColor: [UIColor redColor],
                         UITextAttributeTextShadowOffset: [NSValue valueWithUIOffset:UIOffsetMake(0.0f, 1.0f)],
                                     UITextAttributeFont: [UIFont fontWithName:@"Helvetica" size:20.0f]
     }];

Earlier than iOS 5:

UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 400, 44)];
label.backgroundColor = [UIColor clearColor];
label.font = [UIFont boldSystemFontOfSize:20.0];
label.shadowColor = [UIColor colorWithWhite:0.0 alpha:0.5];
label.textAlignment = UITextAlignmentCenter;
label.textColor =[UIColor whiteColor];
label.text=self.title;	
self.navigationItem.titleView = label;		
[label release];

If you wanted to change the font in the Interface Builder itself (without any code) here is the way to do it in Xcode6:

1.) Find the Navigation Bar view under the Navigation Controller Scene

2.) Change the Title Font, Color and Shadow attributes in the Attributes Inspector.

The above answer works. I would add the following line before the last line. If I don't, it seems the label is center-aligned incorrectly if there is a back button on the left side but no right button.

...
[self.navigationItem.titleView sizeToFit]; 
[label release]; // not needed if you are using ARC

Updated for iOS 7:

[[UINavigationBar appearance] setTitleTextAttributes: [NSDictionary dictionaryWithObjectsAndKeys:
                                                      [UIColor colorWithRed:245.0/255.0 green:245.0/255.0 blue:245.0/255.0 alpha:1.0], NSForegroundColorAttributeName,
                                                      shadow, NSShadowAttributeName,
                                                      [UIFont fontWithName:@"HelveticaNeue-CondensedBlack" size:21.0], NSFontAttributeName, nil]];

courtesy of:

http://www.appcoda.com/customize-navigation-status-bar-ios-7/

Not sure why all the answers included the shadow. Adding the lines that manipulate the shadow does nothing in respect to changing text font. These 2 lines of code will work for iOS 8.4 and Swift

let attributesDictionary = [NSFontAttributeName: UIFont(name: "Helvetica Neue", size: 14)!]
navigationController!.navigationBar.titleTextAttributes = attributesDictionary

The titleTextAttributes stores a dictionary that will dictate the font, color, size, and other attributes of the navigation bar's title.

As of iOS 5 you can use the appearance proxy.

The answer is in a duplicate of this question: https://stackoverflow.com/a/12364740/883413

     NSShadow *shadow = [NSShadow new];
[shadow setShadowColor: [UIColor clearColor]];
[shadow setShadowOffset: CGSizeMake(0.0f, 1.0f)];

[self.navigationController.navigationBar setTitleTextAttributes:[NSDictionary dictionaryWithObjectsAndKeys:
                                         [UIFont fontWithName:@"TimeBurner" size:27.0f], NSFontAttributeName,
                                         [UIColor whiteColor], NSForegroundColorAttributeName,
                                         shadow, NSShadowAttributeName,nil]];