The 20-year-old comes in to provide competition for Jack Rose between the sticks and is the Saddlers' 10th signing since Matt Taylor's arrival as boss earlier this summer.
He is yet to make a senior appearance at professional level but was involved in all three of Brighton Under-21s' games in the Papa John's Trophy last season – against Leyton Orient, Wimbledon and Charlton.
"I'm buzzing with the move. My agent was speaking to me and Brighton were speaking to me about how this move could potentially be on offer, and ever since I heard that I was always wanting to come here," said Rushworth.
"I’ve seen the stadium now and I’ve spoken to the head coach, and I know what his plan is and how he wants to go about it with a lot of new players coming in as well. I am really looking forward to being a part of it.
“I like the fact that the head coach wants to play out from the back. That is one of my main attributes as a goalkeeper.
“I like to play the pretty football, but I can also go long when I need to, and I want to show that I’m not just lumping the ball up and playing the ugly side of the game all the time.”
Rushworth joined Brighton from Halifax two years ago and enjoyed a loan spell at Worthing in 2019/20.
Taylor is looking forward to seeing how he develops at the Banks's Stadium.
"Carl is somebody who came to our attention early on in the recruitment process for a goalkeeper,” said Taylor.
“He fits the ethos of the football club, the way that we want to play next season and he is going to provide good competition in that position.
“We knew that we needed to strengthen in that area, and we are extremely happy that Carl has chosen to pick Walsall as his first loan as he begins his professional career in the mens game."
Taylor added: “It’s important not just for the goalkeepers to have competition but that we have competition all over the pitch.
“What we are striving to get at this football club are players that push each other on a daily basis, players that when they’re in the team are not comfortable because they have always got somebody behind them pushing them extremely hard.
“We’re delighted that Carl has decided to join us over other options that he had.”