Unusual cylindrical magnetic bubble domains completely bounded by domain walls have been stabilized inside YbFe03platelets with high surface coercivities. The energy density of the walls forming the cylinder ends manifests itself as an effective bias field, which, for platelet thicknesses between 55–75&mgr;, stabilizes bubbles in zero applied field. Annealing at 700°C for one hour reduced the coercivity associated with bubble propagation to 0.25 Oe. A theoretical analysis of the stability and coercivity of these self‐biased bubbles is given.