We present a new class of two-dimensional (in x and t) theoretically invariant optical wave packets characterized by a spatiotemporal Bessel function (STB beams). This particular field distribution induces a balance between the diffraction and the dispersion of the pulse. The solution describing the propagation of the STB beam is independent of the propagation distance, but the infinite dimensions of this beam make it impossible to generate. We can limit the dimensions of this beam by the use of a Gaussian envelope, resulting in a spatiotemporal Bessel-Gauss beam (STBG beam), that we can generate experimentally. We present an experimental setup used to generate STBG beams and an experimental autocorrelation trace which is in good agreement with that of theoretical STBG beams.