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.

TMZ obtained video showing RiRi looking sophisticated as she saunters up to the L.A. Superior Court building in downtown L.A.

Check it out ... RiRi is wearing a classy suit and jacket as she walks inside the courthouse with two guys -- one of whom appears to be her muscle.

We're told A$AP and his team of lawyers -- headed up by high-powered attorney Joe Tacopina -- were already inside the courtroom with everyone else.

Looks like Rihanna was trying to slip inside undetected ... but that clearly didn't happen this time around.

In today's proceedings, a little bit of drama ... just before the lunch break, Tacopina got into a heated screaming match with a prosecutor. That's when Rocky -- who had walked over to give Rihanna a kiss -- literally had to hold JT back from getting into the prosecution's face. Rihanna then left the courtroom.

As you know, Rihanna's been showing up at court the last two days to support Rocky -- her longtime partner -- during his assault trial, watching his former friend, A$AP Relli, testify against him. She's been sitting with Rocky's mother and sister in the gallery with the public.

Prosecutors have charged Rocky with shooting Relli during a heated argument on an L.A. sidewalk in 2021.

Until today, Rihanna's been able to fly under the radar of photographers covering the trial. Sorry RiRi ... can't win 'em all!