The other half (Upper Lough Mask) is much deeper, sinking to a long trench with depths in excess of 50 metres.

[citation needed] According to a side-note on the manuscript containing the oldest copy of 'Tóruigheacht Dhiarmada agus Ghráinne' ("The Pursuit of Diarmuid and Gráinne") (Royal Irish Academy Ms. 24.P.9), Irish scribe Dáibhídh Bacach ("lame David") Ó Duibhgeannáin was living and working on Oileán Ruadh ('Red Island') on Lough Mask in the house of Tadhg Og O Flaherty on 1 April 1651.

[citation needed] The "Lough Mask Murders" of 1882 were a notorious incident in the Land War in which a grandfather and grandson acting as bailiffs were killed by tenant farmers and their bodies dumped in the lake.

The World Cup Trout Fly Fishing Championship takes place annually on Lough Mask at Cushlough Bay near Ballinrobe.

"Loch Measca" was taken as the pen-name of Séan Seoighe (John Joyce) in Eachtra múinteóra an Irish-language memoir published in 1929.