KENO-VI is a new version of the KENO Monte Carlo criticality safety code developed at Oak Ridge National Laboratory. It constructs and processes geometry data as sets of quadratic equations. A lengthy set of simple, easy-to-use geometric functions, similar to those provided in KENO-V.a, and the ability to build more complex geometric shapes (represented by sets of quadratic equations) are the heart of the geometry package in KENO-VI. The code’s flexibility is increased by allowing the following features: intersecting geometry regions; hexagonal as well as cuboidal arrays; regions, HOLEs, arrays, and units rotated to any angle and truncated to any position; and the use of an array boundary that intersects the array. KENO-VI maintains all the flexibility and options of KENO-V.a plus a variety of new options. In KENO-VI, units can be constructed using both the simple geometric shapes provided and the tailored geometric shapes constructed using quadratic equations. It includes the new 2-D color plotting capability that has been added to KENO-V.a. Users should be aware that the added geometry features in KENO-VI can result in significantly longer run times than KENO-V.a. A KENO-VI problem that can also be modeled with KENO-V.a will typically run 4 times as long as the same problem using KENO-V.a. Thus the new version VI is not a replacement for the existing version V.a, but an additional version for complex geometries that could not be modeled previously.