Spectroscopy and Ground-State Transfer of Ultracold Bosonic <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:mtext> </mml:mtext> <mml:msup> <mml:mrow> <mml:mmultiscripts> <mml:mrow> <mml:mi mathvariant="norma

We report the creation of ultracold samples of ^{39}K^{133}Cs molecules in their rovibrational ground state. By investigating potentially suitable excited states using one- and two-photon spectroscopy, we have identified a pathway to the ground state via an exceptionally narrow intermediate state. Using stimulated Raman adiabatic passage, we create trapped samples of up to 3500 molecules at temperatures of 1 μK with one-way efficiencies of 71%. The lifetime of these samples is limited by a near-universal two-body loss process, which could shed new light on similar loss mechanisms in other molecular species. Our results are a step toward establishing an alternative molecular species as a platform for the study of bosonic and fermionic quantum matter with strong dipolar interactions.