CRISPR-Cas nucleases are powerful tools to manipulate nucleic acids; however, targeted insertion of DNA remains a challenge as it requires host cell repair machinery. Here we characterize a CRISPR-associated transposase (CAST) from cyanobacteria Scytonema hofmanni which consists of Tn7-like transposase subunits and the type V-K CRISPR effector (Cas12k). ShCAST catalyzes RNA-guided DNA transposition by unidirectionally inserting segments of DNA 60-66 bp downstream of the protospacer. ShCAST integrates DNA into unique sites in the E. coli genome with frequencies of up to 80% without positive selection. This work expands our understanding of the functional diversity of CRISPR-Cas systems and establishes a paradigm for precision DNA insertion.