It said Yussef al-Agha died in Khan Yunis in the collapse of a "resistance tunnel", the type dug for military operations against Israel.
Last year, 22 members of Hamas's armed wing were killed "preparing equipment", the majority in a string of tunnel collapses, the group said last month.
Israel accuses Gaza militants of building tunnels for use to launch attacks against the Jewish state, and destroyed several during a devastating 2014 war with Hamas.
It says Hamas has since been rebuilding the network.
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"Attack tunnels" were a key weapon for Hamas during the last conflict in 2014, with a number of surprise raids inside Israeli territory.
Egypt, which shares a border with Gaza, has also destroyed tunnels Palestinians use to smuggle commercial goods, cash, people and allegedly weapons.
Several Palestinians were also killed last year in tunnel collapses on southern Gaza's border with Egypt.