The maps, which date back to 1589, are thought to be the earliest surviving representations of the naval battles and were completed by an unknown draughtsman, possibly from the Netherlands.
They were sold to an overseas buyer in July but an export ban was imposed on the 10 hand-drawn maps depicting the famous battle of 1588.
In order to prevent their sale abroad, the Portsmouth-based museum raised £600,000 in just eight weeks through public donations and grants of £212,800 from the National Heritage Memorial Fund and £200,000 from the Art Fund.
Professor Dominic Tweddle, the museum’s director general, said: “Like many cultural and heritage institutions 2020 was an exceptionally tough year but we rallied and I am incredibly proud that we have made sure that the armada maps have been saved for generations to come.
“I would take this opportunity to place on record my gratitude to all those who answered our call to help. It was an amazing response from our funding partners and the public, who dug deep in extremely difficult times, to save these treasures.”
A museum spokeswoman added: “These 10 ink and watercolour armada maps present a defining moment in England’s national and naval history.
“They depict in real time a navy defending England’s shores against invasion by the 16th century’s imperial super-power of Spain, with each map detailing the position in the Channel of individual ships in the English and Spanish fleets.
“The defeat of the armada and the 16th century’s superpower was a turning point in forging England’s complex identity as it developed into the modern age.
“The maps offer the opportunity to explore the role of the navy throughout history as a protector of an island nation.”
Culture Minister Caroline Dinenage, who imposed the export ban until January and called for an institution to raise funds, said the maps were an “important piece of British heritage” that act as a reminder of the pivotal naval battle.
“The export bar system exists so we can keep nationally important works in the country and I am delighted that, thanks to the tireless work of the National Museum of the Royal Navy, the armada maps will now go on display to educate and inspire future generations,” said Ms Dinenage.
Rene Olivieri, interim chairman of the National Heritage Memorial Fund, said: “By safeguarding them from export, we can ensure that these maps remain in the UK as they have done since the 16th century.”
The National Museum of the Royal Navy has now launched a new fundraising drive to place the maps on display when it reopens after lockdown with longer term plans for them to tour the country.
Sarah Philp, director of programme and policy for Art Fund, added: “Art Fund is so pleased to help save these irreplaceable maps for the nation, which not only evoke an iconic event in the history of England, but prompt reflection on the influence that history has on the present day.”