From un- + ending.

unending

1. Not ending; having no end; eternal.
   • 1886 October – 1887 January, H[enry] Rider Haggard, She: A History of Adventure, London: Longmans, Green, and Co., published 1887, →OCLC ↗:

     At any rate I was very sure that I would not attempt to attain unending life.

• (having no end) termless; see also Thesaurus:endless

• end
• ending
• unendingly
• unendingness

• French: éternel, sans fin, infini
• German: endlos, nicht enden wollend, ewig
• Spanish: interminable