BRZEGI, Poland — Pope Francis challenged hundreds of thousands of young people who gathered in a Polish meadow to reject being ‘‘couch potatoes’’ who retreat into video games and computer screens and instead engage in social activism and politics to create a more just world.

Peppering his speech with contemporary lingo, the 79-year-old pope, despite a long day of public appearances, addressed his eager audience with enthusiasm Saturday on a warm summer night.

Francis spoke of a paralysis that comes from merely seeking convenience, and from confusing happiness with a complacent way of life that could end up depriving people of the ability to determine their own futures.

‘‘Dear young people, we didn’t come into this world to ‘vegetate,’’ to take it easy, to make our lives a comfortable sofa to fall asleep on. No, we came for another reason: To leave a mark,’’ Francis told a crowd that Polish media estimated at more than 1 million.

He spoke in a huge field in Brzegi, a village outside the southern city of Krakow.

Francis decried a modern escape into consumerism and computers that isolates people. The same theme ran through a ballet performance at the site before his speech: a lonely woman seeks human connections but is rebuffed by people on computer tablets and cellphones until one man emerges from behind a see-through barrier to connect.

‘‘Following Jesus demands a good dose of courage, a readiness to trade in the sofa for a pair of walking shoes and to set out on new and uncharted paths,’’ Francis said.

He challenged his sea of listeners to become engaged as ‘‘politicians, thinkers, social activists’’ and to help build a world economy that is ‘‘inspired by solidarity.’’

‘‘The pope does not order us to do things, he encourages us,’’ said Szymon Werner, a 32-year-old who heard the speech. ‘‘It’s true, there are many temptations, weaknesses in life and we should try to do something about them.’’

‘‘I will give more attention to my family,’’ he vowed.

Francis’ evening appeal came hours after he celebrated a Mass with priests, nuns, and young seminarians, whom he also urged to leave their comfort zones and tend to the needy in the world.

The pope will end his visit to Poland on Sunday after another Mass in Brzegi.