If you have a handgun or are thinking about purchasing one and have never been taught by someone knowledgeable of handguns AND who can provide good instruction the answer is, yes.  You need at least a basic pistol class. If you have some experience shooting, know how to handle handguns safely but are not happy with how well you shoot you may benefit from a refresher on the basics and the integrated act of firing one well aimed shot.

If you have a handgun and are thinking of including it in your personal protection strategy at home or have already done so and have not received solid instruction in how to use one in self-defense then the answer is yes again.  You need to learn how to apply defensive shooting techniques that are not often addressed in basic pistol courses.

If you plan to carry in public and you have not been taught how to do that safely and how to safely get the pistol out of the holster and hit what you need to hit and nothing else then the answer again is yes.

With respect to defensive shooting courses, all of the ones offered by the NRA and my own include content beyond just shooting and presentation skills.  Considerable time is spent in those courses addressing how you can avoid situations in which you might have to actually shoot in self-defense.  The only gunfight you really win is the one you can safely avoid.

Larry Mudgett of Marksmanship Matters has taken the time to address the subject of the need for training.  In that posting he addresses many of the reasons that people give for NOT taking pistol instruction and has kindly granted me permission to link to his website.  You can click here to see if your favorite is among them.  The appearance of this link does not imply an endorsement of me or my courses.

Where you get your training is, of course entirely up to you.   I hope that after you have reviewed my qualifications and the content and price of my courses that you will decide to allow me to be your instructor, however if you decide not to take one of my courses please find another qualified instructor.  You will be safer and more comfortable and competent when handling and shooting pistols if someone teaches you the safe and correct way to do that.