New Zealand's Walsh bags fourth world indoor gold
The 34-year-old, who previously won world indoor golds in 2016, 2018 and 2025, managed a best of 21.82 metres with his sixth attempt.
The two-time Olympic bronze medallist had moved into pole position with his fifth effort of 21.66m, and eventually finished 18cm ahead of American silver medallist Jordan Geist (21.64m).
A second American, Roger Steen, rounded out the podium with a best of 21.49m.
"My whole career started in Poland with bronze at the 2014 world indoors in Sopot," said Walsh, who also bagged a bronze in 2022 and a silver in 2024 to go along with his quartet of golds.
"If you told me then that I would still be here winning medals at every edition since then I would tell you you were dreaming.
"It is great to see I can still do it against the younger guys."
Walsh, who was also crowned world outdoor champion in London in 2017, added: "My goal for today was to throw 22m and win a medal. I did not quite get to 22 but I won gold so it is pretty good.
"I was glad I was able to build things up as the competition went on. Throwing last when you know you have won sometimes saps the energy out of you but, at other times, it can give you a boost, and that happened for me today."
De Sousa wins LJ
Portugal's Sao Tome-born Agate de Sousa won the women's long jump with a best of 6.92m, with just two finals in the morning session of the third and final day of competition in the Polish city.
Italy's Larissa Iapichino claimed silver, just 5cm adrift, with Colombia's Natalia Linares rounding out the podium (6.80).
"Today, I did not think about my opponents and, in my mind, just competed with myself and nobody else," said De Sousa.
"I came here to jump seven metres and that was all I had in my mind. It did not come today but I know that it will come again."
The closing session of the world indoors later Sunday sees Keely Hodgkinson carrying British hopes for a second gold medal after that of Josh Kerr - in the men's 3,000m - when she runs in the women's 800m.
There are also finals in the men's long jump, 800m and 1,500m.
Women's finals comprise the pole vault, the 1,500m, the 60m hurdles and the denouement of the pentathlon, with American Anna Hall and Sofie Dokter of the Netherlands going head-to-head.
There are also finals for both sexes in the 4x400m relays to round off a bumper 12-medal event day.