Local poll results '˜real springboard' for Scottish Lib Dems
The Liberal Democrats saw 67 councillors returned across Scotland, down slightly from the 71 seats the party won in 2012.
But Mr Rennie said his party had been “strongest” in areas where it is targeting the SNP in the June 8 General Election.
The Liberal Democrats are seeking to retake the Edinburgh West seat, and also hope former UK government minister Jo Swinson can oust John Nicolson from East Dunbartonshire, after he took the seat from her in 2015.
Local government elections on Thursday saw the Lib Dems win more than 6,000 votes in the Almond ward area of Edinburgh West, Mr Rennie said, adding this was “the highest number by any candidate from any party in any ward in Scotland since 1994”.
The Scottish Liberal Democrat leader said: “The results like this across Scotland are a real springboard to beat the SNP where we are challenging them on June 8.
“East Dunbartonshire, Argyll, Caithness and North East Fife were superb. We made gains in Gordon and Ross, Skye and Lochaber too.
“Our pro-UK, pro-Europe message with investment in education and mental health is strongest in the seats we are challenging the SNP at Westminster.”
Prior to 2015, the Lib Dems had 11 Scottish MPs at Westminster, but the SNP landslide in the last general election saw the party lose all but one of those, with Ms Swinson, Charles Kennedy and Danny Alexander amongst those who were toppled.
Christine Jardine, who is fighting the Edinburgh West seat for the Liberal Democrats, said: “Our fantastic council results in the Edinburgh West wards have given us the perfect start to the General Election campaign to regain the seat from the SNP.”
Lib Dem election campaign manager and Edinburgh West MSP Alex Cole-Hamilton said: “This election is a straight fight between the Liberal Democrats and the SNP.
“The people of Edinburgh West face a simple choice. Continue to be let down by the SNP, who have shown that they only put independence first, or elect an MP who will truly represent them at Westminster.
“Edinburgh West has a proud history of Liberal Democrat MPs and come June 8 we fully intend to take it back from the SNP.”