how many loyalist survivors from the horus heresy are still alive in 42k

The short answer is: very few. In 42k, the only clearly established loyalist Horus Heresy-era Astartes still “alive” are mostly tied to exceptional cases like dreadnoughts or other unusual survival states, with Bjorn the Fell-Handed being the best-known example.

What seems confirmed

• Bjorn the Fell-Handed is the most famous loyalist survivor still active in the 41st/42nd millennium, preserved in a dreadnought chassis and kept in stasis between wars.

• A few other names are sometimes mentioned in fan discussions, but those lists are inconsistent and often mix up later interments, non-loyalists, or characters not actually alive since the Heresy.

Why the number is so low

The Horus Heresy was over 10,000 years ago in-setting, so even Space Marines who survived the war usually died long before the current era. For a loyalist from that time to still be around, they typically need one of the setting’s extreme exceptions: dreadnought life support, stasis, warp/time anomalies, or similarly unusual circumstances.

Practical answer

If you mean “named loyalist Astartes from the Heresy era who are definitely still around in 42k” , the safest answer is one to a very small handful , depending on how strictly you define “alive”. If you include broader edge cases like missing primarchs, stasis sleepers, or unusual warp-displaced survivors, the list gets messier fast.

Tiny caveat

Forum discussions on this topic often disagree because the setting is full of contradictions, retcons, and ambiguous status labels like “alive,” “missing,” “slumbering,” or “technically extant”.

TL;DR: For loyalist Horus Heresy survivors in 42k, think “basically one famous confirmed case, maybe a few more depending on interpretation,” not dozens.