This chapter introduces the fundamental principles of magnetostatics, the study of magnetic fields produced by stationary electric currents. It begins by establishing the empirical observation that moving electric charges exert a magnetic interaction on each other, distinct from the electrostatic force. This leads to the definition of the magnetic field ( \(\textbf{B}\) ) as a vector field that mediates these interactions. A central concept is the Lorentz force, which describes the total force experienced by a charged particle in the presence of both electric and magnetic fields ( \(\textbf{F}=q(\textbf{E}+\textbf{v}\times \textbf{B}\) )). The chapter presents the dynamics of charged particles under the influence of uniform magnetic fields, including circular motion (cyclotron motion) and helical trajectories, and discusses applications in particle accelerators (cyclotrons and synchrotrons) and magnetic confinement. The Hall effect is presented as a direct consequence of the Lorentz force, explaining the generation of a transverse electric field in current-carrying conductors subjected to a magnetic field, and its various technological applications. The chapter also introduces the Penning trap, a device that uses combined electric and magnetic fields to confine charged particles in three dimensions. The core of magnetostatics is then formalized with Biot–Savart law, which provides a method for calculating the magnetic field generated by continuous current distributions (volume currents) and, more specifically, by current-carrying wires. The chapter illustrates how to visualize magnetic fields through magnetic field lines, emphasizing their characteristic closed-loop nature. Finally, the Laplace force is derived, describing the force exerted by an external magnetic field on a current-carrying wire, and its implications for closed current loops in uniform magnetic fields.