"I Don't Like Mondays" is a song by Irish band The Boomtown Rats that was a number one single in the UK Singles Chart for four weeks during the summer of 1979, and ranks as the sixth biggest British hit of 1979. Written by Bob Geldof, it was the band's second number one single.

According to Geldof, he wrote the song after reading a telex report at Georgia State University's campus radio station, WRAS, on the shooting spree of 16-year-old Brenda Ann Spencer, who fired at children in a school playground at Grover Cleveland Elementary School in San Diego, California, US on 29 January 1979, killing two adults and injuring eight children and one police officer. Spencer showed no remorse for her crime and her full explanation for her actions was "I don't like Mondays. This livens up the day". The song was first performed less than a month later.

Geldof explained how he wrote the song:

I was doing a radio interview in Atlanta with [Johnnie] Fingers and there was a telex machine beside me. I read it as it came out. Not liking Mondays as a reason for doing somebody in is a bit strange. I was thinking about it on the way back to the hotel and I just said 'Silicon chip inside her head had switched to overload'. I wrote that down. And the journalists interviewing her said, 'Tell me why?' It was such a senseless act. It was the perfect senseless act and this was the perfect senseless reason for doing it. So perhaps I wrote the perfect senseless song to illustrate it. It wasn't an attempt to exploit tragedy.

Geldof had originally intended the song as a B-side, but changed his mind after the song was successful with audiences on the Rats' US tour. Spencer's family tried unsuccessfully to prevent the single from being released in the United States. Despite being a major hit in the United Kingdom, it only reached #73 on the US Billboard Hot 100. The song was played regularly by album-oriented rock format radio stations in the United States throughout the 1980s, although radio stations in San Diego refrained from playing the track for some years in respect to local sensitivities about the shooting.

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