Which mammal has the longest whiskers?

It is that group of mammals known as pinnipeds: seals, sea lions and walruses.

Of these animals, the award goes to The Antarctic Fur Seal whose vibrissae measure about 48 cm (19") from base to tip. The full span exceeds one metre in length (39").

The walrus is the pinniped with the most whiskers, having anywhere between 400 and 700 on its face.

https://www.guinnessworldrecords.com/world-records/601926-longest-whiskers-on-a-pinniped