This chapter discusses Physical Layer Security (PLS) for the Sixth Generation (6G) mobile communication standard. It focuses on security against passive adversaries, while active attacks are only mentioned where necessary. The wiretap channel is introduced, as are methods for measuring security and coding schemes to achieve it. Implementations of such schemes for the Additive White Gaussian Noise (AWGN) and fading wiretap channels are presented, along with a statistical analysis of the security achieved. Moreover, it is discussed how to achieve PLS in multimode fiber-optic interconnects. Finally, secret key generation is introduced, and an important application, physical unclonable functions, is presented.