Experimental ionization cross sections for K‐shell by protons in target atoms from beryllium to uranium available in the literature from 1953 to 1999 (nearly 5400 values) are collected to deduce the semi‐empirical K‐shell ionization cross sections by fitting the experimental data normalized to their corresponding theoretical values based on the ECPSSR model which accounts for Coulomb deflection, Energy loss of the projectile, Perturbed Stationary State and Relativistic effects, as a function of the reduced velocity parameter. Our results are compared with the experimental data and with the ECPSSR values and reference ionization cross sections obtained by Paul and Sacher [H. Paul and J. Sacher, At. Data. Nucl. Data. Tables1989, 42, 105]. Copyright © 2010 John Wiley & Sons, Ltd.