The Battleship is an Atomic Era naval ranged unit in Civilization VI. It upgrades from the Frigate (or its replacements) and requires Coal.
In the Summer 2017 Update, the Battleship's 
Anti-Air Strength was increased from 65 to 70.
- Attributes:
Strategy
The Battleship is the backbone of the Atomic Era fleet. Bristling with guns, clad in armor, it has longer range than any previous unit in the game, which not only allows it to attack targets far inland, but also to bombard Coastal cities from a safe distance! This (and the fact that it does full damage against cities) effectively turns it into a naval siege engine.
The Battleship can also defend against aerial attacks, and it is the first ship of the modern fleet that can do so. This makes it very important to acquire as early as possible, especially if potential enemies are developing air power. The problem is that the Battleship requires a strategic resource - Coal, just like the Ironclad. If you haven't managed to acquire it somehow, your entire fleet will remain stuck in the Renaissance Era!
Should you find yourself facing off with Battleships, try to hammer them with as much air power as you can muster. They still have anti-air capabilities, so they must be dealt with if you want to ensure air superiority!
Civilopedia entry
The evolution of the dreadnought that dominated the waves of the early 20th Century was the battleship … bigger, faster, with bigger guns and thicker armor, able to sink anything else (including each other) afloat with a single salvo. The first “true” battleships to see action appeared at Jutland in 1916 AD, where – mixed with a motley collection of dreadnoughts and battle-cruisers – the German and British ones fought to a draw. In the inter-war years, the battleship evolved into the behemoth of popular thought, despite the Washington Naval Treaty of 1922 and other bits of international paper that tried to limit their size and armament. Not only was WW2 the golden age of the battleship – and all the best known sailed those troubled times: Bismarck, Hood, Arizona, Yamato, and Missouri among many others – it also witnessed its demise. By the end warplanes, submarines, radar-guided missiles and other technological marvels had relegated battleships to floating shore batteries and rusting tourist attractions.
Trivia
The Battleship's model is based on the Iowa-class battleships that the U.S. Navy used during World War II.