Rihanna could only escape the paparazzi for so long at A$AP Rocky's L.A. trial ... the singing sensation was recorded today heading inside the courthouse with a bodyguard.

If convicted at trial of both counts as charged, Rocky — whose real name is Rakim Mayers — faces up to 24 years in prison.

Pop star Rihanna returned to a downtown Los Angeles courtroom Thursday and watched the alleged victim in the assault trial of her boyfriend A$AP Rocky become increasingly contentious on the witness ...