The powerful 23-year-old centre joins the Saints from Western Province, whom he helped win the 2014 Currie Cup. A Junior World Championship winner with South Africa in 2012, Howard spent three months earlier this season with Munster, for whom he played in both the Pro 12 and European Rugby Champions Cup.
He returned home to Cape Town to join the Stormers' squad ahead of the Super Rugby campaign, but will be heading north to join his new team mates for their Aviva Premiership and Champions Cup campaigns.
“Pat is a young player who has shown plenty of promise in the Currie Cup, Pro 12 and Champions Cup,” commented director of rugby Jim Mallinder.
“We've been impressed by what we've seen, but believe that there is more to come from him and are looking forward to seeing Pat develop in our squad.”
“I really enjoyed my time in Europe earlier this year and was delighted when Saints showed interest in me,” Howard added. “It is a great opportunity for me to be joining a fantastic club and continue to develop as a player.
“I cannot wait to pull on the Saints jersey!
“I have had a great time coming through the ranks at Western Province, but feel that now is the right time to experience something new overseas.”