A two-dimensional X-ray diffractometer uses an X-ray source that emits a divergent beam toward a sample under test. The divergent beam has a substantially fixed width in a first direction perpendicular to its propagation direction, and a thickness in a second direction perpendicular to the propagation direction that increases proportionally to a distance from the source. An aperture may be used to block a portion of the beam in the second direction, and the sample is positioned so that the beam illuminates a two-dimensional area of the sample surface. The detector detects an X-ray signal diffracted from the sample across a two-dimensional detection area, and may use a one-dimensional detector array that collects diffracted X-ray signal at a number of different positions. The source, detector and sample may be mounted to a goniometer to maintain them in a desired relative orientation.