Yes. Could be the drive in the transmission. Could be the electrics in the instrument cluster. Always post your model year, early cars had the old fashioned cable drive, later cars were electronic.
Of course you could be one of the lucky ones and a wire has dropped off or broken.
If the transmission drive breaks it is very tricky to fix without pulling the transmission, it can sometimes be done by an experienced mechanic who knows how it's done. If the instrument cluster is at fault then it is a simple enough job to replace but time consuming. Also a new part is likely NLA. Source a used part from a reliable source.
Would be nice to know what year, type of Saab and type of transaxle you have.
If you have a manual transmission, there are several sources of this problem. One is an external speedo gear transducer that inserts at the top of the transaxle and plugs into a harness. This can be removed with a single torx screw for inspection. You test it by inserting the drive end into a drill and reversing the drill to see if it has any effect on the speedo. If no effect, you might need to replace this gear. They cost about $20.
If that works fine, your problem might be the $2 internal speedo gear. You need to remove the transaxle and completely strip it to replace the gear. At that point, most people opt for a rebuild since all the trouble parts are exposed.