Rock mechanics, which is related to geomechanics and rock engineering, is an exciting applied geology topic that is central to geological, mining, civil, and petroleum engineering. It is about how and why rocks fail, at both the field scale (rock masses), as well as laboratory, and with important applications to surface slopes, underground excavations, and dam and bridge foundations. This Jahns lecture is an introduction to rock mechanics that I have given to newly entering Mining and Geological Engineering students at the University of Arizona. It includes the topics of rock strength, stresses in rock masses, discontinuities, field characterization, rock mass classification, factor of safety and probability of failure, and some slope and underground examples. It will also cover the important topics of new field technologies and numerical modeling. This talk would be of interest to students in college or university departments that do not offer a full rock mechanics course (other than topics offered in a structural geology class). I also talk about job opportunities for students with skills in rock mechanics, and mention important rock mechanics conferences that they can attend, as well as the student chapter sponsored by the American Rock Mechanics & Geomechanics Association (ARMA).