The singer-songwriter wrote a loving tribute to JJ in a since deleted Instagram post, thanking Janet for breathing continued life into her dreams while saying she's always looked up to her.

She wrote the emotional message on a screengrab of Jackson' self-titled album, "Janet" released back in 1993.

While it might have just been an innocuous tribute post to another music legend, Britney's got some common ground with Janet ... in that Justin Timberlake won't apologize to either of them.

Remember ... during a show in New York City at the end of last month, Justin told the crowd he was going to apologize to "absolutely f***ing nobody" before singing "Cry Me A River" -- a clear dig at Brit, but Janet fans assumed that meant her as well.

Justin and Janet will be forever linked for their fateful 2004 Super Bowl Halftime show where Justin ripped Jackson's costume revealing one of her breasts to the crowd -- something he chalked up to an accident at the time.

However, he apologized to both Britney and Janet back in 2021 ... after the documentary "Framing Britney Spears" aired on Hulu, saying he had inadvertently benefited from misogynistic institutions and felt he needed to say sorry for that.

Of course, Britney and Justin have been on especially bad terms after the fake-out apology ... with Spears basically calling Timberlake a crybaby in a basketball-related post.

Maybe Britney's trying to collect allies in her war with JT ... or maybe she's just sending love to a fellow artist.

Either way, Britney's post certainly got fans' eyebrows raised.