An article of footwear comprising: an upper for an article of footwear; and a sole structure, wherein the upper, the sole structure, or both the upper and the sole structure comprise a bladder (1036, 3100), the bladder comprising a first film (31 10a) secured to a second film to define a sealed internal cavity; and a fluid disposed within the sealed internal cavity at a pressure of one atmosphere (101 kilopascals) or greater; wherein the first film, or the second film, or each of the first film and the second film is a multi-layered film (1076, 2160) including a core region comprising at least 20 gas-barrier layers and a plurality of elastomeric layers, wherein the gas-barrier layers alternate with the elastomeric layers, wherein each of the gas-barrier layers has an average thickness in a range of from about 0.01 micrometers to about 0.75 micrometers and comprises at least one gas-barrier material, and wherein each of the elastomeric layers has an average thickness in a range of from about 2 micrometers to about 8 micrometers and comprises at least one elastomeric material, and wherein the core region has a total thickness less than 200 micrometers. an upper for an article of footwear; and a sole structure, wherein the upper, the sole structure, or both the upper and the sole structure comprise a bladder (1036, 3100), the bladder comprising a first film (31 10a) secured to a second film to define a sealed internal cavity; and a fluid disposed within the sealed internal cavity at a pressure of one atmosphere (101 kilopascals) or greater; wherein the first film, or the second film, or each of the first film and the second film is a multi-layered film (1076, 2160) including a core region comprising at least 20 gas-barrier layers and a plurality of elastomeric layers, wherein the gas-barrier layers alternate with the elastomeric layers, wherein each of the gas-barrier layers has an average thickness in a range of from about 0.01 micrometers to about 0.75 micrometers and comprises at least one gas-barrier material, and wherein each of the elastomeric layers has an average thickness in a range of from about 2 micrometers to about 8 micrometers and comprises at least one elastomeric material, and wherein the core region has a total thickness less than 200 micrometers. a first film (31 10a) secured to a second film to define a sealed internal cavity; and a fluid disposed within the sealed internal cavity at a pressure of one atmosphere (101 kilopascals) or greater; wherein the first film, or the second film, or each of the first film and the second film is a multi-layered film (1076, 2160) including a core region comprising at least 20 gas-barrier layers and a plurality of elastomeric layers, wherein the gas-barrier layers alternate with the elastomeric layers, wherein each of the gas-barrier layers has an average thickness in a range of from about 0.01 micrometers to about 0.75 micrometers and comprises at least one gas-barrier material, and wherein each of the elastomeric layers has an average thickness in a range of from about 2 micrometers to about 8 micrometers and comprises at least one elastomeric material, and wherein the core region has a total thickness less than 200 micrometers.