The recombination rate constant for the NH2((XB1)-B-2) + NH2((XB1)-B-2) --> N2H4(X(1)A(1)) reaction in He, Ne, Ar, and N-2 was measured over the pressure range 1-20 Torr at a temperature of 296 K. The NH2 radical was produced by 193 nm laser photolysis of NH3 dilute in the third-body gas. The production of NH2 and the loss of NH3 were monitored by high-resolution continuous-wave absorption spectroscopy: NH2 on the (1)2(21) <-- (1)3(31) rotational transition of the (0,7,0)A(2)A(1) <-- (0,0,0) (XB1)-B-2 vibronic band and NH3 on either inversion doublet of the (q)Q(3)(3) rotational transition of the nu(1) fundamental. Both species were detected simultaneously following the photolysis laser pulse. The broader Doppler width of the NH2 spectral transition allowed temporal concentration measurements to be extended up to 20 Torr before pressure broadening effects became significant. Fall-off behavior was identified and the bimolecular rate constants for each collision partner were fit to a simple Troe form defined by the parameters, k(0), k(inf), and F-cent. This work is the first part of a two part series in which part 2 will discuss the measurements with more efficient energy transfer collision partners CH4, C2H6, CO2, CF4, and SF6. The pressure range was too limited to extract any new information on k(inf), and k(inf) was taken from the theoretical calculations of Klippenstein et al. (J. Phys. Chem A 2009, 113, 10241) as k(inf) = 7.9 x 10(-11) cm(3) molecule(-1) s(-1) at 296 K. The individual Troe parameters were: He, k(0) = 2.8 x 10(-29) and F-cent = 0.47; Ne, k(0) = 2.7 x 10(-29) and F-cent = 0.34; Ar, k(0) = 4.4 x 10(-29) and F-cent = 0.41; N-2, k(0) = 5.7 x 10(-29) and F-cent = 0.61, with units cm(6) molecule(-2) s(-1) for k(0). In the case of N-2 as the third body, it was possible to measure the recombination rate constant for the NH2 + H reaction near 20 Torr total pressure. The pure three-body recombination rate constant was (2.3 +/- 0.55) x 1(0-)3 cm(6) molecule(-2) s(-1), where the uncertainty is the total experimental uncertainty including systematic errors at the 2 sigma level of confidence.