McCartney, who also designed the sports kits for Team GB, based the looks on the signature silhouettes that commonly feature in her fashion designs, with a focus on tailoring for both the men's and women's outfits.
Each piece will feature a specially designed coat of arms by the College of Arms, which provides the basis for the iconography across the UK's entire Olympics and Paralympics range.
For the female athletes, McCartney designed a sporty navy-blue dress made from a high-performance perforated fabric. This is paired with a white tailored jacket embroidered with a custom coat of arms, and a statement belt with a metal buckle.
Male athletes will wear a navy-blue pea coat with military-inspired detailing. Underneath, tailored white shorts are paired with a blue shirt made from poplin fabric, which features a white coat of arms embroidered on the breast pocket.
McCartney, who is creative director at Adidas, was also responsible for the team's kit in 2012. But this is the first time the designer has created outfits for the opening ceremony.
"The goal for Rio 2016 was to rewrite the rules of performance and design for athletes, allowing them to look and feel like champions on and off the field," she said.
"The inspiration behind the design was this idea of contrasting British tradition with a modern attitude."
"The new Coat Of Arms, specially commissioned for this project, and traditional Union Flag hues sit alongside bold textures and modern silhouettes to create a strong identity and make the athletes feel like a team," she added.
This year's Olympic games takes place from 5 August to 21 August.
In the run-up to the games, Rio's preparation has been heavily scrutinised. Last week, the Rio 2016 organising committee admitted that 19 of the 31 towers that make up the Athletes Village had yet to pass full checks.
Flooding, broken elevators, mould and ceiling holes have reportedly caused the Australian team to temporarily relocate, while the Italian and Dutch contingents have also voiced concerns.
A boat ramp designed for sailing competitions at the Olympics in Rio de Janeiro also collapsed just days ahead of the games' opening ceremony.