Since the complex number $\left(- \frac {1}{2}+ \frac { \sqrt {3}}{2}i\right)^{2}=- \frac {1}{2}- \frac { \sqrt {3}}{2}i$,
the coordinates of the point corresponding to this complex number in the complex plane are $\left(- \frac {1}{2},- \frac { \sqrt {3}}{2}\right)$.
Therefore, the point is located in the third quadrant of the complex plane.
Hence, the correct answer is $\boxed{\text{C}}$.
First, perform the exponentiation of the complex number, organize the result into the standard form of a complex number's algebraic expression, and identify the coordinates of the corresponding point to determine its location.
This question examines the algebraic representation of complex numbers and their geometric meaning. The key to solving this question is to organize the complex number into its standard algebraic form. This is a basic question.