Stockholm's OMXS index rose 0.04 on Thursday and closed at 630.4, a historically high level. It broke a previous record set in April.
Anglo-Swedish pharmaceutical company Astra Zeneca led the way – steaming ahead by 2.6 percent.
Sweden's major banks also received a boost when the US Federal Reserved indicated it would not cut interest rates further this year.
Swedbank gained up to 1.7 percent, Nordea 1.3 percent and SEB and Handelsbanken 0.1 percent.
Swedish steel giant SSAB went in the opposite direction, falling 3.3 percent after US Steel late on Wednesday warned of worse results ahead.
European markets were also buoyant on Thursday. Paris' CAC40 index gained 0.7 percent, London's FTSE 0.6 percent and DAX in Frankfurt 0.5 percent.