U.S. Treasury yields fell sharply Friday as a flight to safety drove global investors into the government securities.

The intraday yield of the benchmark 30-year bond fell to a record of 1.889%, well below the previous all-time low of 1.905% in late August, according to data from Tradeweb. The bond yield later rebounded to close at 1.917%, still down from 1.971% on Thursday.

Treasurys...