Ysbyty Alltwen (English: Alltwen Hospital) is a health facility in Tremadog, Gwynedd, Wales.

It is managed by the Betsi Cadwaladr University Health Board.

The facility was commissioned to replace the aging Ysbyty Bron y Garth in Penrhyndeudraeth.

[1] It was designed by IBI Group and built on an elevated site which had previously been occupied by a rail interchange and ironstone mine.

[2] It cost £19 million to construct and was officially opened by Edwina Hart, Minister for Health and Social Services, in July 2009.