Fifteen healthy participants were included in this randomized and balanced within-subject study investigating the global and local changes in functional connectivity following intravenous injection of lysergic acid diethylamide (LSD) and their correlation with subjective reports of ego dissolution. Participants were administered intravenous LSD (75 µg) or placebo in a balanced order in two different sessions with a washout period of at least two weeks between sessions. Subjective drug effects were assessed using 6 visual analogue scale (VAS) items and the 11 factor altered states of consciousness (ASC) questionnaire, and functional connectivity was measured using fMRI scans. Increases in global functional connectivity under LSD were observed in the bilateral thalamus, as well as the frontal, parietal, and inferior temporal cortices, regions which also showed high 5-HT2A receptor densities. This increase in connectivity observed under LSD also correlated with subjective reports of ego dissolution.