| Champ: |  Sloane Stephens |
| Runner: | Jeļena Ostapenko |
| Score: | 7–6(7–5), 6–1 |
| Draw: | 96 |
| Seeds: | 32 |
| Before Name: | Miami Open – Women's singles |
| After Name: | Miami Open – Women's singles |
See main article: 2018 Miami Open.
Sloane Stephens defeated Jeļena Ostapenko in the final, 7–6(7–5), 6–1 to win the women's singles tennis title at the 2018 Miami Open. It was Stephens' sixth career singles title, first Premier Mandatory title, and first title since winning the US Open in September 2017. By virtue of her victory, Stephens also made her debut in the Top 10, at No. 9.
Johanna Konta was the defending champion, but lost in the fourth round to Venus Williams.
Danielle Collins became the first qualifier in Miami Open history to reach the semifinals.[1]
All seeds received a bye into the second round.