A sole structure for an article of footwear, the sole structure comprising: a fluid-filled chamber including a barrier formed from a polymer material, the barrier forming an exterior of the fluid-filled chamber and defining an interior cavity that contains a pressurized fluid, the barrier comprising a first barrier portion, an opposite second barrier portion and a sidewall barrier portion, the sidewall barrier portion (i) extending around a periphery of the chamber, (ii) being formed by the second barrier portion, and (iii) being joined to the first barrier portion at a peripheral bond located around an upper portion of the fluid-filled chamber at an end of the sidewall barrier portion; and a tether element disposed within the interior cavity and including an upper plate secured to an inner surface of the first barrier portion, an opposite lower plate secured to an inner surface of the second barrier portion, and a plurality of tethers extending between and secured to the upper plate and the lower plate, the plurality of tethers spacing the upper plate and the lower plate apart from each other, the upper plate being contoured to have a non-planar configuration, wherein the contour of the upper plate forms a depression in a central area of the upper plate, wherein the central area is centrally located between a medial side of the sole structure and a lateral side of the sole structure, characterized in that a stiffness of the upper plate is greater than a stiffness of the material forming the first barrier portion and the second barrier portion; and a stiffness of the lower plate is greater than a stiffness of the material forming the first barrier portion and the second barrier portion. a fluid-filled chamber including a barrier formed from a polymer material, the barrier forming an exterior of the fluid-filled chamber and defining an interior cavity that contains a pressurized fluid, the barrier comprising a first barrier portion, an opposite second barrier portion and a sidewall barrier portion, the sidewall barrier portion (i) extending around a periphery of the chamber, (ii) being formed by the second barrier portion, and (iii) being joined to the first barrier portion at a peripheral bond located around an upper portion of the fluid-filled chamber at an end of the sidewall barrier portion; and a tether element disposed within the interior cavity and including an upper plate secured to an inner surface of the first barrier portion, an opposite lower plate secured to an inner surface of the second barrier portion, and a plurality of tethers extending between and secured to the upper plate and the lower plate, the plurality of tethers spacing the upper plate and the lower plate apart from each other, the upper plate being contoured to have a non-planar configuration, wherein the contour of the upper plate forms a depression in a central area of the upper plate, wherein the central area is centrally located between a medial side of the sole structure and a lateral side of the sole structure, characterized in that a stiffness of the upper plate is greater than a stiffness of the material forming the first barrier portion and the second barrier portion; and a stiffness of the lower plate is greater than a stiffness of the material forming the first barrier portion and the second barrier portion.