Background: Preeclampsia affects five to ten percent of pregnant women and accounts for about twelve percent of maternal mortality. It is the third most common cause of maternal mortality worldwide. Papilledema is an indirect and late indicator of raised intracranial pressure (ICP), whereas a pressure rise in optic nerve sheath (and the resulting enlargement of the optic nerve diameter) is a more dynamic process. The retrobulbar optic nerve sheath diameter (ONSD) can be measured at a position 3 mm posterior to the globe, where ultrasound contrast is greatest with more reproducible results. Objective: To evaluate the correlation between ultrasonographic measurement of ONSD with the degree of severity of preeclampsia. Patients and methods: This prospective observational study was conducted at Mansoura University Hospital Intensive Care Unit from July 2019 to June 2020. Just after delivery, 175 pregnant females aged between 18 and 45 years old were enrolled for participating in this study. Out of them, 25 females were excluded. Results: As regarding body weight, there was a significant difference between the control group (79.9±6.36 kg) and preeclamptic without severe feature group (87.7±10.58 kg). The mean body weight in severe preeclampsia group was (91.5 ±14.73kg) which showed no significant difference from that of the non-severe group. ONSD values showed significant difference between the studied groups. The control group had ONSD mean value of 4.85±0.32 mm, mild preeclamptic group had mean value of 6.05±0.096 mm, while severe preeclampsia group had a mean value of 6.76±0.25 mm. Conclusion: Ultrasonographic measurement of ONSD provides a non-invasive, quick and readily accessible tool for evaluation of raised intracranial pressure (ICP).