Base Set was the first Pokémon Trading Card Game expansion released in English. It introduced the trading-card version of the original Pokémon roster to English-speaking markets.
The English Base Set launched in the United States in January 1999. It contained 102 cards, including Pokémon, Energy, and Trainer cards. Its most famous card is the holographic Charizard, which became one of the most recognizable and sought-after cards in the hobby.
The Japanese trading-card game began earlier, with the first Japanese set released in October 1996. That set is commonly referred to in English as the Base Expansion Pack. Because the Japanese and English release schedules and naming conventions differ, “first set” can produce different answers unless the language is specified.
Jungle, Fossil, and Team Rocket were later English expansions. Base Set is therefore the precise answer for the first English expansion, while the broader Japanese trading-card game had already begun several years before the Pokémon franchise reached its 30th anniversary.