Foldable armrest sofa and single chair

A Foldable armrest, comprising an armrest body, wherein the armrest body comprises an outer side plate and an inner side plate that are capable of being folded in a width direction of the armrest body;

• a width adjusting mechanism is connected between the outer side plate and the inner side plate;
• the width adjusting mechanism comprises locking kits and at least one adjusting rod;
• the locking kits are connected with the inner side plate, the at least one adjusting rods are connected with the outer side plate, and the locking kits and the adjusting rods are interlocked in the width direction of the armrest body;
• when the outer side plate and the inner side plate move away from each other in the width direction of the armrest body, the width adjusting mechanism extends in the width direction of the armrest body, and when the outer side plate and the inner side plate move closer to each other in the width direction of the armrest body, the width adjusting mechanism retracts in the width direction of the armrest body.