sites is as strong as the on-site interactions now commonly realized with atoms. This longer range interaction for polar molecules will allow access to a new regime of strongly corre- lated quantum gases with unique phase transitions, such as to supersolid phases for bosons [17, 18] and to topological superfluid phases for fermions [19]. Another important differ- ence between magnetic and electric dipolar interactions is that the strength of the effective electric dipole moment is tunable with an applied electric field. In addition to its obvious utility for controlling the interaction strength in dipolar quantum gases, the electric-field dependence could be exploited in the development of novel quantum computing schemes or in the control of ultracold chemical reactions. We perform our experiments with an ultracold gas of $^{40}$K$^{87}$Rb molecules prepared in a single nuclear hyperfine state within the ro-vibronic ground state ( $^{1}$Σ$^{+}$) [10, 20]. The gas is confined in a pancake-shaped optical dipole trap, which is realized by overlapping two horizontally propagating, elliptically shaped laser beams with a wavelength of λ = 1064 nm. Typical harmonic trapping frequencies are ω$_{x}$ = 2 π × 40 Hz and ω$_{z}$ = 2 π × 280 Hz, in the horizontal and vertical directions, respectively. The KRb molecules have a permanent electric dipole moment of 0.57 Debye [10], where 1 Debye = 3 . 336 × 10 − 30 C m. However, the effective molecular dipole moment in the lab frame is zero in the absence of an external electric field. When an external electric field is applied, the molecules begin to align with the field, and have an induced dipole moment, d , that increases as shown in the inset of Fig. 1 B. This figure covers the range of applied electric field that we currently access experimentally, which corresponds to an accessible dipole moment range of 0 to 0 . 22 Debye. In our setup, the external electric field points in the vertical direction (ˆ z ), parallel to the tight axis of the optical trap. Thus, the spatially anisotropic dipolar interactions will be predominantly repulsive for molecules colliding in the horizontal direction (side-by-side) and predominantly attractive for molecules approaching each other along the vertical direction (head-to-tail). In an ultracold gas, the quantum statistics of the particles plays an essential role in the interactions. Our $^{40}$K$^{87}$Rb molecules are fermions prepared in a single internal quantum state at a temperature equal to 1.4 times the Fermi temperature. Therefore, the quantum statistics requires that the wave function for two colliding molecules be antisymmetric with respect to molecule exchange. If one considers the relative angular momentum between two colliding molecules, this means that scattering can only proceed via odd partial waves, and will be dominated by angular momentum L = 1 ( p -wave) scattering at ultralow tempera- 3