Onelli Glacier, Glacier in Los Glaciares National Park, Argentina

Onelli Glacier is an ice formation in the Patagonian Andes that releases meltwater into Lake Argentino. The ice mass covers a large area and forms a white landscape surrounded by mountain peaks.

The glacier was named after an Italian scientist who came to Argentina in the late 1800s and studied the landscapes of this region. His work helped document the geological features of the Southern Patagonian Ice Field.

The glacier is named after Clemente Onelli (1864–1924), an Italian explorer-naturalist who emigrated to Argentina in 1889 and worked with Perito Moreno at the La Plata Museum. Financed by Ramón Santamarina and Manuel Lainez, he explored Lake Argentino and published Trepando los Andes in 1904.

Onelli Glacier drains into Onelli Bay, an arm of Lake Argentino reached by boat from the park's southern sector. The ice is seen from the water rather than on foot, and the bay is often visited together with the nearby Upsala Glacier. The glacier is retreating, so the front and the floating ice change from year to year.

The Bolado Glacier was once connected to this ice formation but separated due to the continuous retreat of both ice masses. This separation shows the dramatic change these formations have undergone in recent decades.