Jonas Greger Walnum (20 August 1771 – 10 March 1838) was a Norwegian property owner and politician.
He resided in the town of Sandnessjøen on the island of Alsta where he was an innkeeper and trader.
In 1801, Walnum acquired the estate of his father-in-law, Jørgen Sverdrup Hersleb, and settled as proprietary of Nord-Herøy, the largest island in Herøy Municipality.
Their eldest son, Jørgen Olaus Hersleb Walnum (1799-1888), became the local chaplain and later took over the family estate on Nord-Herøy.
[2][3][4] Jonas Walnum was elected to the Norwegian Parliament in 1824, representing the constituency of Nordland.