The biggest winners of 2025's artificial intelligence boom were not the stocks plastered across headlines.
While retail investors piled into Nvidia, five lesser-known infrastructure companies quietly delivered returns that left the chip giant in the dust. Lumentum, Celestica, Western Digital, Seagate, and Micron, names rarely mentioned at dinner tables, each more than tripled in value this year, according to CNBC data.
For everyday investors who spent 2025 chasing the obvious play, the message is uncomfortable but clear: the real money was hiding in plain sight.
The Stocks You Overlooked
Nvidia remains the undisputed face of the AI revolution, having soared roughly thirteenfold since the end of 2022 to a staggering market capitalisation of $4.6T (£3.4T), CNBC reported. Yet in 2025 alone, its gains paled against a group of suppliers that power the infrastructure behind the hype.
Lumentum, a San Jose-based maker of optical switches and transceivers for fibre-optic cables, surged 372% this year. The company's sales jumped 58% in its most recent quarter to $533M (£395M), with 60% of revenue now flowing from cloud and AI infrastructure.
'Our growth is powered by AI demand spanning our laser chips and optical transceivers inside data centres, as well as the interconnected long-haul networks that link them,' Lumentum CEO Michael Hurlston said on an earnings call, as reported by CNBC.
Western Digital, a 55-year-old hard drive manufacturer rarely associated with cutting-edge technology, climbed nearly 300%. Seagate, its longtime rival, rose 231%. Both companies have capitalised on an often-ignored reality: artificial intelligence models require vast amounts of storage.
'Data is the fuel that powers AI, and it is HDDs that provide the most reliable, scalable and cost-effective data storage solution,' Western Digital CEO Irving Tan said in October, citing a hospital using AI to analyse $7B medical images, according to CNBC.
Why This Matters for Your Portfolio
The gains were not random. With four of the world's largest technology firms projecting collective expenditures of $380B (£282B) on data centre and infrastructure buildouts this year, Wall Street has quietly rotated into the vendors supplying memory, storage, networking equipment, and optical connections.
Micron Technology, the only major US-based memory producer, saw its stock climb 241% after exceeding Wall Street estimates. The company is 'more than sold out' of its high-bandwidth memory chips, according to business chief Sumit Sadana. Demand grew so intense that Micron shuttered its consumer-focused product line in December to prioritise AI customers, CNBC reported.
According to CNBC, Morgan Stanley analysts noted that Micron's results showed the best revenue and profit upside in 'the history of the US semis industry', aside from Nvidia.
Celestica, a Toronto-headquartered network switch maker, rounded out the group with gains exceeding 230%. The company supplies components for Google's custom AI chips and is scheduled to begin mass production of parts for liquid-cooled rack-scale computers next year, according to CEO Robert Mionis.
What Comes Next
However, the gains come with a warning. Analysts expect growth to slow significantly across all five companies by 2027, with Micron's revenue expansion projected to collapse from around double digits this fiscal year to less than 1% by 2028, according to LSEG data cited by CNBC.
Seagate faces particular scepticism. Despite its 233% rally, the stock carries an average 12-month price target suggesting just 0.22% potential upside, according to MarketBeat data reported by The Globe and Mail. Short interest has surged 197% year-on-year, signalling that bears are circling.
For investors who missed the 2025 rally, the lesson is not to chase yesterday's winners but to ask where the next overlooked opportunity lies, before it triples without you.
Disclaimer: Our digital media content is for informational purposes only and does not constitute investment advice. Please conduct your own analysis or seek professional guidance before investing. Remember, investments are subject to market risks, and past performance does not guarantee future results.
