The European Union proposed a bloc-wide common charging standard for smartphones and other electronic devices, a move that, if adopted, would effectively bar the use of Apple Inc.’s unique “Lightning” charging port now used for all of its new smartphones.

The proposal calls for all electronics sold in the EU to use the same type of charging port, the so-called “USB-C” format, which is already widespread among laptop computers, Android phones and many other non-Apple devices. Some Apple Mac computers have USB-C chargers but...

The European Union proposed a bloc-wide common charging standard for smartphones and other electronic devices, a move that, if adopted, would effectively bar the use of Apple Inc.’s unique “Lightning” charging port now used for all of its new smartphones.

The proposal calls for all electronics sold in the EU to use the same type of charging port, the so-called “USB-C” format, which is already widespread among laptop computers, Android phones and many other non-Apple devices. Some Apple Mac computers have USB-C chargers but its iPhones don’t. They would have to be redesigned to comply with the proposed regulations.

Legislation mandating the change would need to be hammered out and approved by the EU’s parliament and member states, a process that could take months. Once green lighted in Brussels, the legislation would direct the EU’s 27 member states to draft binding legislation to effect the change. The proposal, announced Thursday, also builds in time for manufacturers to adopt the changes, meaning it could be 2024 at the earliest before the rule takes effect.

Apple said it opposes the proposal, saying such a mandate would stifle innovation.

The proposal comes at a time when Brussels has targeted Apple and other Silicon Valley giants over a host of regulatory, tax and oversight issues. Separate legislation proposed late last year by European Commission Executive Vice President Margarethe Vestager targets alleged anticompetitive behavior by large tech companies, and could impose new obligations for moderating content on big companies—backed by huge fines. Another EU proposal would add new rules about the handling of corporate and government data in the bloc.

This week’s proposal opens a new front for the EU in consumer hardware, after more than a decade of trying to push manufacturers to standardize chargers on their own through voluntary commitments. Ms. Vestager said the proposal comes amid consumer frustration about incompatible chargers for smartphone and mobile devices and concern over waste in the bloc, where she said 420 million smartphones and other devices were sold last year.

“European consumers were frustrated long enough about incompatible chargers piling up in their drawers,” she said in a press release. “We gave industry plenty of time to come up with their own solutions, now time is ripe for legislative action for a common charger.”

Apple said such a mandate would hurt innovation and have the opposite effect on electronic waste, making more of it rather than reducing it. In a statement early Friday, Apple said the proposal could “disrupt a thriving ecosystem, create electronic waste, and greatly inconvenience users.”

If the proposal is approved by EU parliamentarians and member states, EU states would be directed to pass their own laws mandating the common charging system within a year and give manufacturers another year to comply. Apple said two years isn’t enough time to make such a change.

Write to Trefor Moss at Trefor.Moss@wsj.com and Sam Schechner at sam.schechner@wsj.com