Hugo
A static site generator written in Go, started in 2013 by Steve Francia. It markets itself on speed and delivers: thousands of pages build in under a second.
It ships as a single binary with no dependencies, which removes the entire class of problems with Ruby versions and npm trees that its competitors suffer from. Content is written in Markdown with front matter; templates use Go's html/template — powerful, but with a syntax few enjoy on first contact. It has built-in taxonomies for tags and categories, shortcodes for embedding components inside Markdown, image processing and multilingual support without add-ons. It suits documentation, blogs and company sites where you want static files to put behind a CDN. Competitors: Jekyll (older, slower), Eleventy (JavaScript), Astro (component-based).