Analysts had predicted Ron Howard's film about a young Han Solo would take between $130m (£97.6m) and $150m (£112.7m) on its debut weekend.
But it had to settle for $103m (£77.4m), which was still enough to knock Deadpool 2 off the top spot.
Solo, starring Alden Ehrenreich, took an estimated $168m (£126.2m) overseas.
The Hollywood Reporter's Pamela McClintock described this figure as "grim".
However, the film was generally praised by critics when reviews first came out.
