The event preceded an EU-India summit where a landmark free trade deal is widely expected to be announced.
Military bands and cavalry units paraded through the capital, with fighter jets and the latest military hardware on display.
Prime Minister Narendra Modi said the occasion “inspires us in our collective resolve to build a developed India”, AFP reported.
European Council President Antonio Costa and European Commission President Ursula von der Leyen attended the parade.
The two sides have been working on a trade agreement for over a decade.
Efforts were expedited last year following US President Donald Trump’s trade tariffs.
Bilateral India-EU trade in goods reached 120 billion euros in 2024, a near 90% increase over the past decade.
The pact is seen as a major win for both Brussels and New Delhi as they seek to counter US tariffs and Chinese export controls.
The EU views India as an important market, while New Delhi sees Brussels as a key source of technology and investment.
Republic Day marks the adoption of India’s post-independence constitution in 1950.
The annual parade is a tightly choreographed spectacle featuring floats from different Indian states.
India is on track to become the world’s fourth-largest economy this year, according to IMF projections.