  Recent measurements of CPT violation and Lorentz symmetry breaking in
$B^0-\bar{B}^0$ mixing and $B^0_s-\bar{B}^0_s$ mixing, obtained from data taken
by the LHCb experiment, are highlighted. The results are expressed in terms of
the Standard-Model Extension (SME) coefficients, which incorporate both CPT and
Lorentz violation. Due to the large boost of the $B$ mesons at LHCb, the SME
coefficients can be determined with high precision. The bounds on these
coefficients are improved significantly compared to previous measurements.
