Kate Middleton's back in the public eye ... appearing at Wimbledon -- her second public appearance since announcing her cancer diagnosis -- and, the crowd gave her a welcome fit for a royal.

The Princess of Wales pulled up to the All England Club Sunday for the men's final between Carlos Alcaraz and Novak Djokovic ... and, check out the clip of her making her way to her seat -- thunderous applause follows.

Her Royal Highness waves to the audience for around 30 seconds while they clap and cheer her ... with many filming the awe-inspiring moment at the stadium.

KM's daughter, Princess Charlotte, sat beside her at the match ... though her husband Prince William and son Prince George missed out on the match to watch a major soccer game in Berlin instead.

Middleton stepped away from her royal duties back in March after disappearing from the public eye before posting a video to social media revealing she'd been diagnosed with cancer.

She did attend the Trooping of the Colour ceremony last month, but her public appearances are few and far between these days.

BTW ... Middleton also awarded Alcaraz with the trophy -- his second in a row -- chatting with the Spanish star after he easily defeated Djokovic in three sets.

Seems Kate's slowly coming out of reclusion ... though it's unclear when she might fully resume her royal duties.