A vehicle seat configured to support an occupant in a sitting position, the seat comprising: a squab, a backrest, and an airbag unit; the airbag unit comprising an inflatable bag having an inlet region (4, 5) and being provided in an initially rolled and/or folded airbag package, and an inflator actuable to direct inflating gas into the airbag via the inlet region (4, 5) to inflate the airbag into an inflated configuration; the airbag comprising an inflatable chamber (8, 9; 208) which, when inflated into a deployed position, defines an inflated shroud which extends over said sitting position and provides lateral protection to said occupant of the seat in said sitting position; characterized in that: the airbag further comprises an inflatable guide, connected to the inflatable chamber (8, 9; 208), the airbag being mounted and configured such that, upon actuation of said inflator to inflate the airbag, said inflatable guide is at least partially inflated before the inflatable chamber (8, 9; 208), thereby initially urging the inflatable chamber (8, 9; 208) away from the backrest of the seat; wherein the airbag is configured such that after the inflatable guide is at least partially inflated, the inflatable chamber (8, 9; 208) inflates into said deployed position; wherein said inflatable guide is formed in a lobe of the airbag; and said inflatable guide is proximate to said inlet region (4, 5). a squab, a backrest, and an airbag unit; the airbag unit comprising an inflatable bag having an inlet region (4, 5) and being provided in an initially rolled and/or folded airbag package, and an inflator actuable to direct inflating gas into the airbag via the inlet region (4, 5) to inflate the airbag into an inflated configuration; the airbag comprising an inflatable chamber (8, 9; 208) which, when inflated into a deployed position, defines an inflated shroud which extends over said sitting position and provides lateral protection to said occupant of the seat in said sitting position; characterized in that: the airbag further comprises an inflatable guide, connected to the inflatable chamber (8, 9; 208), the airbag being mounted and configured such that, upon actuation of said inflator to inflate the airbag, said inflatable guide is at least partially inflated before the inflatable chamber (8, 9; 208), thereby initially urging the inflatable chamber (8, 9; 208) away from the backrest of the seat; wherein the airbag is configured such that after the inflatable guide is at least partially inflated, the inflatable chamber (8, 9; 208) inflates into said deployed position; wherein said inflatable guide is formed in a lobe of the airbag; and said inflatable guide is proximate to said inlet region (4, 5). the airbag further comprises an inflatable guide, connected to the inflatable chamber (8, 9; 208), the airbag being mounted and configured such that, upon actuation of said inflator to inflate the airbag, said inflatable guide is at least partially inflated before the inflatable chamber (8, 9; 208), thereby initially urging the inflatable chamber (8, 9; 208) away from the backrest of the seat; wherein the airbag is configured such that after the inflatable guide is at least partially inflated, the inflatable chamber (8, 9; 208) inflates into said deployed position; wherein said inflatable guide is formed in a lobe of the airbag; and said inflatable guide is proximate to said inlet region (4, 5).